Isolate more pat9125 code

Remove probing from Marlin_main and move it into pat9125_probe so that
it can support the various variants.

Firmware/Marlin_main.cpp

@@ -88,18 +88,13 @@
 #include "la10compat.h"
 #endif
 
-#ifdef SWSPI
-#include "swspi.h"
-#endif //SWSPI
-
 #include "spi.h"
 
-#ifdef SWI2C
-#include "swi2c.h"
-#endif //SWI2C
-
 #ifdef FILAMENT_SENSOR
 #include "fsensor.h"
+#ifdef IR_SENSOR
+#include "pat9125.h" // for pat9125_probe
+#endif
 #endif //FILAMENT_SENSOR
 
 #ifdef TMC2130
@@ -864,9 +859,7 @@ static void check_if_fw_is_on_right_printer(){
 #ifdef FILAMENT_SENSOR
   if((PRINTER_TYPE == PRINTER_MK3) || (PRINTER_TYPE == PRINTER_MK3S)){
     #ifdef IR_SENSOR
-    swi2c_init();
-    const uint8_t pat9125_detected = swi2c_readByte_A8(PAT9125_I2C_ADDR,0x00,NULL);
-      if (pat9125_detected){
+      if (pat9125_probe()){
         lcd_show_fullscreen_message_and_wait_P(_i("MK3S firmware detected on MK3 printer"));}////c=20 r=3
     #endif //IR_SENSOR
 

Firmware/config.h

@@ -23,7 +23,6 @@
 #define ADC_CALLBACK      adc_ready //callback function ()
 
 //SWI2C configuration
-#define SWI2C
 //#define SWI2C_SDA         20 //SDA on P3
 //#define SWI2C_SCL         21 //SCL on P3
 #define SWI2C_A8
@@ -31,7 +30,10 @@
 #define SWI2C_TMO         2048 //2048 cycles timeout
 
 //PAT9125 configuration
+//#define PAT9125_SWSPI
 #define PAT9125_SWI2C
+//#define PAT9125_I2C
+
 #define PAT9125_I2C_ADDR  0x75  //ID=LO
 //#define PAT9125_I2C_ADDR  0x79  //ID=HI
 //#define PAT9125_I2C_ADDR  0x73  //ID=NC

Firmware/pat9125.c

@@ -26,12 +26,15 @@
 #define PAT9125_BANK_SELECTION	0x7f
 
 
-#ifdef PAT9125_SWSPI
+#if defined(PAT9125_SWSPI)
 #include "swspi.h"
-#endif //PAT9125_SWSPI
-#ifdef PAT9125_SWI2C
+#elif defined(PAT9125_SWI2C)
 #include "swi2c.h"
-#endif //PAT9125_SWI2C
+#elif defined(PAT9125_I2C)
+#error not implemented
+#else
+#error unknown PAT9125 communication method
+#endif
 
 
 uint8_t pat9125_PID1 = 0;
@@ -103,14 +106,30 @@ extern FILE _uartout;
 #define uartout (&_uartout)
 
 
+uint8_t pat9125_probe()
+{
+#if defined(PAT9125_SWSPI)
+    swspi_init();
+    //#error not implemented
+#elif defined(PAT9125_SWI2C)
+    swi2c_init();
+    return swi2c_readByte_A8(PAT9125_I2C_ADDR,0x00,NULL);
+#elif defined(PAT9125_I2C)
+    twi_init();
+  #ifdef IR_SENSOR
+    // NOTE: this is called from the MK3S variant, so it should be kept minimal
+    #error not implemented
+  #else
+	return pat9125_rd_reg(PAT9125_PID1) != 0;
+  #endif
+#endif
+}
+
 uint8_t pat9125_init(void)
 {
-#ifdef PAT9125_SWSPI
-	swspi_init();
-#endif //PAT9125_SWSPI
-#ifdef PAT9125_SWI2C
-	swi2c_init();
-#endif //PAT9125_SWI2C
+    if (!pat9125_probe())
+        return 0;
+
 	// Verify that the sensor responds with its correct product ID.
 	pat9125_PID1 = pat9125_rd_reg(PAT9125_PID1);
 	pat9125_PID2 = pat9125_rd_reg(PAT9125_PID2);

Firmware/pat9125.h

@@ -18,6 +18,7 @@ extern int16_t pat9125_y;
 extern uint8_t pat9125_b;
 extern uint8_t pat9125_s;
 
+extern uint8_t pat9125_probe(void);     // Return non-zero if PAT9125 can be trivially detected
 extern uint8_t pat9125_init(void);
 extern uint8_t pat9125_update(void);    // update all sensor data
 extern uint8_t pat9125_update_y(void);  // update _y only