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@@ -1,5 +1,5 @@
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/*
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- twi.c - TWI/I2C library for Wiring & Arduino
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+ twi.c - Stripped-down TWI/I2C library
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Copyright (c) 2006 Nicholas Zambetti. All right reserved.
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This library is free software; you can redistribute it and/or
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@@ -20,11 +20,6 @@
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*/
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#include <math.h>
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-#include <stdlib.h>
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-#include <inttypes.h>
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-#include <avr/io.h>
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-#include <avr/interrupt.h>
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-#include <compat/twi.h>
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#include "Arduino.h" // for digitalWrite
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#ifndef cbi
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@@ -35,43 +30,11 @@
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#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
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#endif
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-#include "pins_arduino.h"
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#include "twi.h"
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-static volatile uint8_t twi_state;
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-static volatile uint8_t twi_slarw;
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-static volatile uint8_t twi_sendStop; // should the transaction end with a stop
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-static volatile uint8_t twi_inRepStart; // in the middle of a repeated start
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-static void (*twi_onSlaveTransmit)(void);
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-static void (*twi_onSlaveReceive)(uint8_t*, int);
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-
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-static uint8_t twi_masterBuffer[TWI_BUFFER_LENGTH];
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-static volatile uint8_t twi_masterBufferIndex;
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-static volatile uint8_t twi_masterBufferLength;
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-
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-static uint8_t twi_txBuffer[TWI_BUFFER_LENGTH];
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-static volatile uint8_t twi_txBufferIndex;
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-static volatile uint8_t twi_txBufferLength;
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-
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-static uint8_t twi_rxBuffer[TWI_BUFFER_LENGTH];
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-static volatile uint8_t twi_rxBufferIndex;
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-
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-static volatile uint8_t twi_error;
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-
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-/*
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- * Function twi_init
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- * Desc readys twi pins and sets twi bitrate
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- * Input none
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- * Output none
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- */
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void twi_init(void)
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{
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- // initialize state
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- twi_state = TWI_READY;
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- twi_sendStop = true; // default value
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- twi_inRepStart = false;
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-
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// activate internal pullups for twi.
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digitalWrite(SDA, 1);
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digitalWrite(SCL, 1);
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@@ -85,477 +48,46 @@ void twi_init(void)
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SCL Frequency = CPU Clock Frequency / (16 + (2 * TWBR))
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note: TWBR should be 10 or higher for master mode
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It is 72 for a 16mhz Wiring board with 100kHz TWI */
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-
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- // enable twi module, acks, and twi interrupt
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- TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA);
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}
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-/*
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- * Function twi_disable
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- * Desc disables twi pins
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- * Input none
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- * Output none
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- */
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void twi_disable(void)
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{
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- // disable twi module, acks, and twi interrupt
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- TWCR &= ~(_BV(TWEN) | _BV(TWIE) | _BV(TWEA));
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-
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// deactivate internal pullups for twi.
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digitalWrite(SDA, 0);
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digitalWrite(SCL, 0);
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}
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-/*
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- * Function twi_slaveInit
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- * Desc sets slave address and enables interrupt
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- * Input none
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- * Output none
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- */
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-void twi_setAddress(uint8_t address)
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+uint8_t twi_waitfor(uint8_t status)
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{
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- // set twi slave address (skip over TWGCE bit)
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- TWAR = address << 1;
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-}
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-
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-/*
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- * Function twi_setClock
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- * Desc sets twi bit rate
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- * Input Clock Frequency
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- * Output none
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- */
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-void twi_setFrequency(uint32_t frequency)
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-{
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- TWBR = ((F_CPU / frequency) - 16) / 2;
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-
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- /* twi bit rate formula from atmega128 manual pg 204
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- SCL Frequency = CPU Clock Frequency / (16 + (2 * TWBR))
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- note: TWBR should be 10 or higher for master mode
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- It is 72 for a 16mhz Wiring board with 100kHz TWI */
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-}
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-
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-/*
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- * Function twi_readFrom
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- * Desc attempts to become twi bus master and read a
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- * series of bytes from a device on the bus
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- * Input address: 7bit i2c device address
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- * data: pointer to byte array
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- * length: number of bytes to read into array
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- * sendStop: Boolean indicating whether to send a stop at the end
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- * Output number of bytes read
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- */
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-uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length, uint8_t sendStop)
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-{
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- uint8_t i;
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-
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- // ensure data will fit into buffer
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- if(TWI_BUFFER_LENGTH < length){
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- return 0;
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- }
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-
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- // wait until twi is ready, become master receiver
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- while(TWI_READY != twi_state){
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- continue;
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- }
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- twi_state = TWI_MRX;
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- twi_sendStop = sendStop;
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- // reset error state (0xFF.. no error occured)
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- twi_error = 0xFF;
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-
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- // initialize buffer iteration vars
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- twi_masterBufferIndex = 0;
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- twi_masterBufferLength = length-1; // This is not intuitive, read on...
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- // On receive, the previously configured ACK/NACK setting is transmitted in
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- // response to the received byte before the interrupt is signalled.
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- // Therefor we must actually set NACK when the _next_ to last byte is
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- // received, causing that NACK to be sent in response to receiving the last
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- // expected byte of data.
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-
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- // build sla+w, slave device address + w bit
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- twi_slarw = TW_READ;
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- twi_slarw |= address << 1;
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-
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- if (true == twi_inRepStart) {
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- // if we're in the repeated start state, then we've already sent the start,
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- // (@@@ we hope), and the TWI statemachine is just waiting for the address byte.
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- // We need to remove ourselves from the repeated start state before we enable interrupts,
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- // since the ISR is ASYNC, and we could get confused if we hit the ISR before cleaning
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- // up. Also, don't enable the START interrupt. There may be one pending from the
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- // repeated start that we sent ourselves, and that would really confuse things.
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- twi_inRepStart = false; // remember, we're dealing with an ASYNC ISR
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- do {
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- TWDR = twi_slarw;
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- } while(TWCR & _BV(TWWC));
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- TWCR = _BV(TWINT) | _BV(TWEA) | _BV(TWEN) | _BV(TWIE); // enable INTs, but not START
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- }
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- else
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- // send start condition
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- TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT) | _BV(TWSTA);
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-
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- // wait for read operation to complete
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- while(TWI_MRX == twi_state){
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- continue;
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- }
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-
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- if (twi_masterBufferIndex < length)
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- length = twi_masterBufferIndex;
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-
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- // copy twi buffer to data
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- for(i = 0; i < length; ++i){
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- data[i] = twi_masterBuffer[i];
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- }
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-
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- return length;
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-}
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-
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-/*
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- * Function twi_writeTo
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- * Desc attempts to become twi bus master and write a
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- * series of bytes to a device on the bus
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- * Input address: 7bit i2c device address
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- * data: pointer to byte array
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- * length: number of bytes in array
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- * wait: boolean indicating to wait for write or not
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- * sendStop: boolean indicating whether or not to send a stop at the end
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- * Output 0 .. success
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- * 1 .. length to long for buffer
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- * 2 .. address send, NACK received
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- * 3 .. data send, NACK received
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- * 4 .. other twi error (lost bus arbitration, bus error, ..)
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- */
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-uint8_t twi_writeTo(uint8_t address, uint8_t* data, uint8_t length, uint8_t wait, uint8_t sendStop)
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-{
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- uint8_t i;
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-
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- // ensure data will fit into buffer
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- if(TWI_BUFFER_LENGTH < length){
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- return 1;
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- }
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-
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- // wait until twi is ready, become master transmitter
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- while(TWI_READY != twi_state){
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- continue;
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- }
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- twi_state = TWI_MTX;
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- twi_sendStop = sendStop;
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- // reset error state (0xFF.. no error occured)
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- twi_error = 0xFF;
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-
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- // initialize buffer iteration vars
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- twi_masterBufferIndex = 0;
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- twi_masterBufferLength = length;
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-
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- // copy data to twi buffer
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- for(i = 0; i < length; ++i){
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- twi_masterBuffer[i] = data[i];
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- }
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-
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- // build sla+w, slave device address + w bit
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- twi_slarw = TW_WRITE;
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- twi_slarw |= address << 1;
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-
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- // if we're in a repeated start, then we've already sent the START
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- // in the ISR. Don't do it again.
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- //
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- if (true == twi_inRepStart) {
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- // if we're in the repeated start state, then we've already sent the start,
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- // (@@@ we hope), and the TWI statemachine is just waiting for the address byte.
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- // We need to remove ourselves from the repeated start state before we enable interrupts,
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- // since the ISR is ASYNC, and we could get confused if we hit the ISR before cleaning
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- // up. Also, don't enable the START interrupt. There may be one pending from the
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- // repeated start that we sent outselves, and that would really confuse things.
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- twi_inRepStart = false; // remember, we're dealing with an ASYNC ISR
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- do {
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- TWDR = twi_slarw;
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- } while(TWCR & _BV(TWWC));
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- TWCR = _BV(TWINT) | _BV(TWEA) | _BV(TWEN) | _BV(TWIE); // enable INTs, but not START
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- }
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- else
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- // send start condition
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- TWCR = _BV(TWINT) | _BV(TWEA) | _BV(TWEN) | _BV(TWIE) | _BV(TWSTA); // enable INTs
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-
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- // wait for write operation to complete
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- while(wait && (TWI_MTX == twi_state)){
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- continue;
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- }
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-
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- if (twi_error == 0xFF)
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- return 0; // success
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- else if (twi_error == TW_MT_SLA_NACK)
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- return 2; // error: address send, nack received
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- else if (twi_error == TW_MT_DATA_NACK)
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- return 3; // error: data send, nack received
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- else
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- return 4; // other twi error
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+ while(!(TWCR & _BV(TWINT)));
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+ return (TW_STATUS != status);
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}
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-/*
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- * Function twi_transmit
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- * Desc fills slave tx buffer with data
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- * must be called in slave tx event callback
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- * Input data: pointer to byte array
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- * length: number of bytes in array
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- * Output 1 length too long for buffer
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- * 2 not slave transmitter
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- * 0 ok
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- */
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-uint8_t twi_transmit(const uint8_t* data, uint8_t length)
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+uint8_t twi_rw8(uint8_t address, uint8_t mode, uint8_t* data)
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{
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- uint8_t i;
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+ // send start condition
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+ TWCR = _BV(TWEN) | _BV(TWINT) | _BV(TWSTA);
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+ if(twi_waitfor(TW_START))
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+ return 1;
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+
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+ // send address
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+ TWDR = mode;
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+ TWDR |= (address << 1);
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+ TWCR = _BV(TWEN) | _BV(TWINT);
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+ if(twi_waitfor(mode == TW_READ? TW_MR_SLA_ACK: TW_MT_SLA_ACK))
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+ return 2;
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+
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+ // send or receive data
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+ if(mode == TW_WRITE)
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+ TWDR = *data;
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+ TWCR = _BV(TWEN) | _BV(TWINT);
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+ if(twi_waitfor(mode == TW_READ? TW_MR_DATA_NACK: TW_MT_DATA_ACK))
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+ return 3;
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+ if(mode == TW_READ)
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+ *data = TWDR;
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+
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+ // send stop
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+ TWCR = _BV(TWEN) | _BV(TWINT) | _BV(TWSTO);
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- // ensure data will fit into buffer
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- if(TWI_BUFFER_LENGTH < (twi_txBufferLength+length)){
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- return 1;
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- }
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-
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- // ensure we are currently a slave transmitter
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- if(TWI_STX != twi_state){
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- return 2;
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- }
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-
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- // set length and copy data into tx buffer
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- for(i = 0; i < length; ++i){
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- twi_txBuffer[twi_txBufferLength+i] = data[i];
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- }
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- twi_txBufferLength += length;
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-
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return 0;
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}
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-
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-/*
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- * Function twi_attachSlaveRxEvent
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- * Desc sets function called before a slave read operation
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- * Input function: callback function to use
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- * Output none
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- */
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-void twi_attachSlaveRxEvent( void (*function)(uint8_t*, int) )
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-{
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- twi_onSlaveReceive = function;
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-}
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-
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-/*
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- * Function twi_attachSlaveTxEvent
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- * Desc sets function called before a slave write operation
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- * Input function: callback function to use
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- * Output none
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- */
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-void twi_attachSlaveTxEvent( void (*function)(void) )
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-{
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- twi_onSlaveTransmit = function;
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-}
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-
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-/*
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- * Function twi_reply
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- * Desc sends byte or readys receive line
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- * Input ack: byte indicating to ack or to nack
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- * Output none
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- */
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-void twi_reply(uint8_t ack)
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-{
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- // transmit master read ready signal, with or without ack
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- if(ack){
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- TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWINT) | _BV(TWEA);
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- }else{
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- TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWINT);
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- }
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-}
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-
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-/*
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- * Function twi_stop
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- * Desc relinquishes bus master status
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- * Input none
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- * Output none
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- */
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-void twi_stop(void)
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-{
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- // send stop condition
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- TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT) | _BV(TWSTO);
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-
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- // wait for stop condition to be exectued on bus
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- // TWINT is not set after a stop condition!
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- while(TWCR & _BV(TWSTO)){
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- continue;
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- }
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-
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- // update twi state
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- twi_state = TWI_READY;
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-}
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-
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-/*
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- * Function twi_releaseBus
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- * Desc releases bus control
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- * Input none
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- * Output none
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- */
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-void twi_releaseBus(void)
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-{
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- // release bus
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- TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT);
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-
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- // update twi state
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- twi_state = TWI_READY;
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-}
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-
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-ISR(TWI_vect)
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-{
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- switch(TW_STATUS){
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- // All Master
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- case TW_START: // sent start condition
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- case TW_REP_START: // sent repeated start condition
|
|
|
- // copy device address and r/w bit to output register and ack
|
|
|
- TWDR = twi_slarw;
|
|
|
- twi_reply(1);
|
|
|
- break;
|
|
|
-
|
|
|
- // Master Transmitter
|
|
|
- case TW_MT_SLA_ACK: // slave receiver acked address
|
|
|
- case TW_MT_DATA_ACK: // slave receiver acked data
|
|
|
- // if there is data to send, send it, otherwise stop
|
|
|
- if(twi_masterBufferIndex < twi_masterBufferLength){
|
|
|
- // copy data to output register and ack
|
|
|
- TWDR = twi_masterBuffer[twi_masterBufferIndex++];
|
|
|
- twi_reply(1);
|
|
|
- }else{
|
|
|
- if (twi_sendStop)
|
|
|
- twi_stop();
|
|
|
- else {
|
|
|
- twi_inRepStart = true; // we're gonna send the START
|
|
|
- // don't enable the interrupt. We'll generate the start, but we
|
|
|
- // avoid handling the interrupt until we're in the next transaction,
|
|
|
- // at the point where we would normally issue the start.
|
|
|
- TWCR = _BV(TWINT) | _BV(TWSTA)| _BV(TWEN) ;
|
|
|
- twi_state = TWI_READY;
|
|
|
- }
|
|
|
- }
|
|
|
- break;
|
|
|
- case TW_MT_SLA_NACK: // address sent, nack received
|
|
|
- twi_error = TW_MT_SLA_NACK;
|
|
|
- twi_stop();
|
|
|
- break;
|
|
|
- case TW_MT_DATA_NACK: // data sent, nack received
|
|
|
- twi_error = TW_MT_DATA_NACK;
|
|
|
- twi_stop();
|
|
|
- break;
|
|
|
- case TW_MT_ARB_LOST: // lost bus arbitration
|
|
|
- twi_error = TW_MT_ARB_LOST;
|
|
|
- twi_releaseBus();
|
|
|
- break;
|
|
|
-
|
|
|
- // Master Receiver
|
|
|
- case TW_MR_DATA_ACK: // data received, ack sent
|
|
|
- // put byte into buffer
|
|
|
- twi_masterBuffer[twi_masterBufferIndex++] = TWDR;
|
|
|
- case TW_MR_SLA_ACK: // address sent, ack received
|
|
|
- // ack if more bytes are expected, otherwise nack
|
|
|
- if(twi_masterBufferIndex < twi_masterBufferLength){
|
|
|
- twi_reply(1);
|
|
|
- }else{
|
|
|
- twi_reply(0);
|
|
|
- }
|
|
|
- break;
|
|
|
- case TW_MR_DATA_NACK: // data received, nack sent
|
|
|
- // put final byte into buffer
|
|
|
- twi_masterBuffer[twi_masterBufferIndex++] = TWDR;
|
|
|
- if (twi_sendStop)
|
|
|
- twi_stop();
|
|
|
- else {
|
|
|
- twi_inRepStart = true; // we're gonna send the START
|
|
|
- // don't enable the interrupt. We'll generate the start, but we
|
|
|
- // avoid handling the interrupt until we're in the next transaction,
|
|
|
- // at the point where we would normally issue the start.
|
|
|
- TWCR = _BV(TWINT) | _BV(TWSTA)| _BV(TWEN) ;
|
|
|
- twi_state = TWI_READY;
|
|
|
- }
|
|
|
- break;
|
|
|
- case TW_MR_SLA_NACK: // address sent, nack received
|
|
|
- twi_stop();
|
|
|
- break;
|
|
|
- // TW_MR_ARB_LOST handled by TW_MT_ARB_LOST case
|
|
|
-
|
|
|
- // Slave Receiver
|
|
|
- case TW_SR_SLA_ACK: // addressed, returned ack
|
|
|
- case TW_SR_GCALL_ACK: // addressed generally, returned ack
|
|
|
- case TW_SR_ARB_LOST_SLA_ACK: // lost arbitration, returned ack
|
|
|
- case TW_SR_ARB_LOST_GCALL_ACK: // lost arbitration, returned ack
|
|
|
- // enter slave receiver mode
|
|
|
- twi_state = TWI_SRX;
|
|
|
- // indicate that rx buffer can be overwritten and ack
|
|
|
- twi_rxBufferIndex = 0;
|
|
|
- twi_reply(1);
|
|
|
- break;
|
|
|
- case TW_SR_DATA_ACK: // data received, returned ack
|
|
|
- case TW_SR_GCALL_DATA_ACK: // data received generally, returned ack
|
|
|
- // if there is still room in the rx buffer
|
|
|
- if(twi_rxBufferIndex < TWI_BUFFER_LENGTH){
|
|
|
- // put byte in buffer and ack
|
|
|
- twi_rxBuffer[twi_rxBufferIndex++] = TWDR;
|
|
|
- twi_reply(1);
|
|
|
- }else{
|
|
|
- // otherwise nack
|
|
|
- twi_reply(0);
|
|
|
- }
|
|
|
- break;
|
|
|
- case TW_SR_STOP: // stop or repeated start condition received
|
|
|
- // ack future responses and leave slave receiver state
|
|
|
- twi_releaseBus();
|
|
|
- // put a null char after data if there's room
|
|
|
- if(twi_rxBufferIndex < TWI_BUFFER_LENGTH){
|
|
|
- twi_rxBuffer[twi_rxBufferIndex] = '\0';
|
|
|
- }
|
|
|
- // callback to user defined callback
|
|
|
- twi_onSlaveReceive(twi_rxBuffer, twi_rxBufferIndex);
|
|
|
- // since we submit rx buffer to "wire" library, we can reset it
|
|
|
- twi_rxBufferIndex = 0;
|
|
|
- break;
|
|
|
- case TW_SR_DATA_NACK: // data received, returned nack
|
|
|
- case TW_SR_GCALL_DATA_NACK: // data received generally, returned nack
|
|
|
- // nack back at master
|
|
|
- twi_reply(0);
|
|
|
- break;
|
|
|
-
|
|
|
- // Slave Transmitter
|
|
|
- case TW_ST_SLA_ACK: // addressed, returned ack
|
|
|
- case TW_ST_ARB_LOST_SLA_ACK: // arbitration lost, returned ack
|
|
|
- // enter slave transmitter mode
|
|
|
- twi_state = TWI_STX;
|
|
|
- // ready the tx buffer index for iteration
|
|
|
- twi_txBufferIndex = 0;
|
|
|
- // set tx buffer length to be zero, to verify if user changes it
|
|
|
- twi_txBufferLength = 0;
|
|
|
- // request for txBuffer to be filled and length to be set
|
|
|
- // note: user must call twi_transmit(bytes, length) to do this
|
|
|
- twi_onSlaveTransmit();
|
|
|
- // if they didn't change buffer & length, initialize it
|
|
|
- if(0 == twi_txBufferLength){
|
|
|
- twi_txBufferLength = 1;
|
|
|
- twi_txBuffer[0] = 0x00;
|
|
|
- }
|
|
|
- // transmit first byte from buffer, fall
|
|
|
- case TW_ST_DATA_ACK: // byte sent, ack returned
|
|
|
- // copy data to output register
|
|
|
- TWDR = twi_txBuffer[twi_txBufferIndex++];
|
|
|
- // if there is more to send, ack, otherwise nack
|
|
|
- if(twi_txBufferIndex < twi_txBufferLength){
|
|
|
- twi_reply(1);
|
|
|
- }else{
|
|
|
- twi_reply(0);
|
|
|
- }
|
|
|
- break;
|
|
|
- case TW_ST_DATA_NACK: // received nack, we are done
|
|
|
- case TW_ST_LAST_DATA: // received ack, but we are done already!
|
|
|
- // ack future responses
|
|
|
- twi_reply(1);
|
|
|
- // leave slave receiver state
|
|
|
- twi_state = TWI_READY;
|
|
|
- break;
|
|
|
-
|
|
|
- // All
|
|
|
- case TW_NO_INFO: // no state information
|
|
|
- break;
|
|
|
- case TW_BUS_ERROR: // bus error, illegal stop/start
|
|
|
- twi_error = TW_BUS_ERROR;
|
|
|
- twi_stop();
|
|
|
- break;
|
|
|
- }
|
|
|
-}
|
|
|
-
|