I2C Master and Slave STM32F401.Nucleo

Questions » I2C Master and Slave STM32F401.Nucleo

Andrey Chepegin

9 years, 5 months ago.

I have 2 boards STM32F401.Nucleo. If on board Slave set waitEnable = 1 => on board Master i2c.write() return failure Why the delay break I2C communication?

DigitalOut led(PA_5);
DigitalOut orange(D8);
DigitalOut green(D9);
DigitalIn  button(PC_13);
Serial pc(USBTX, USBRX); // tx, rx

I2C           i2c(PB_9,PB_8);         // SDA, SCL
I2CSlave  slave(PB_3,PB_10);   // SDA, SCL
const int  addr = 0x04;
char MasterTX[] = "Message from Master";
char MasterRX[64] = {0};
char SlaveTX[] = "Message from Slave";
char SlaveRX[64] = {0};
int  waitEnable = 0;

#ifdef MASTER
while(1) {
   nRet = i2c.write(addr,MasterTX,sizeof(MasterTX),true);
   if (nRet == 0) {     // Slave ack
      orange = 1;
      green = 0;
   } else {             // Slave nack
      orange = 0;
      green = 1;
   }	
   led = 1;
   wait(0.5);
   led = 0;
   wait(0.5);			
}			
#else
   int nCounter = 0;
   slave.address(addr);
   while(1) {
      if (waitEnable == 1) {
         wait(0.01);
      }
      led = 1;
				
      memset(SlaveTX,0,sizeof(SlaveRX));
      step = slave.receive();
      switch(step) {
         case I2CSlave::ReadAddressed:   // Master запрашивает ответ от Slave
            slave.write(SlaveTX,sizeof(SlaveTX));
            printf("TX: %s\r\n",SlaveTX);
            orange = 1;
         break;
			
         case I2CSlave::WriteGeneral:    // Бродкаст
            slave.read(SlaveRX,sizeof(SlaveRX));
            printf("Broadcast RX: %s\r\n",SlaveRX);
            orange = 1;
         break;
			
         case I2CSlave::WriteAddressed: // Master спрашивает текущий Slave
           slave.read(SlaveRX,sizeof(SlaveRX));
           printf("Slave RX %d: %s\r\n",nCounter,SlaveRX);
           orange = 1;
         break;
			
         case I2CSlave::NoData:
            orange = 0;
         break;
      }		
      nCounter++;
  }		
#endif

Update: The problem was a bad pull-up SDA and SCL. Now I use an external power supply for the Nucleo boards and pull-up lines.

A new problem: Slave receives the message "Message from Master" correctly. Master receives incorrect.

Init MasterRX = "ProbaOdnako". Slave transmit "123\0". If there is no delay in Master between nRet = i2c.write(addr,MasterTX,sizeof(MasterTX)) and nRet = i2c.read(addr,MasterRX,4) nRet = i2c.read(addr,MasterRX,4) return "яяяяaOdnako".

With delay sometimes nRet = i2c.read(addr,MasterRX,4) return "я123aOdnako". nRet = i2c.read(addr,MasterRX,4) return "123".

Why sometimes appears first symbol 'я' (0xFF)? What values should be a delay between the functions write and read?

New code:

#include "Global.h"
#include "main.h"

DigitalOut led(PA_5);
DigitalOut orange(D7);
DigitalOut green(D9);
DigitalIn  button(PC_13);
Serial pc(USBTX, USBRX); // tx, rx
Serial uart(PA_9, PA_10);  // tx, rx 
Timer timer;

#define ARRAY_SIZE   24
I2C       i2c(PB_9,PB_8);   // SDA, SCL
I2CSlave  slave(PB_3,PB_10);   // SDA, SCL
int i;
int step;
int  nRet = 1;
int  waitEnable = 0;
const int  addr = 0xA0;
char nameDevice[16] = {0};
char MasterTX[] = "Message яяяя Master";
char SlaveTX[] = "Message from Slave";
char MasterRX[sizeof(SlaveTX)] = {0};
char SlaveRX[sizeof(MasterTX)] = {0};
int nCounter = 0;

#define MASTER		
int main() {
	led = 0;
	green = 0;
	orange = 0;
	uart.baud(9600);
	//pc.printf("SystemCoreClock = %d Hz\n", SystemCoreClock);
	
#ifdef MASTER		
	int  search = 0;
	strcpy(nameDevice,"Master");
  uart.printf("Uart start %s\r\n",nameDevice);
	
	i2c.frequency(100000); //Set the clock frequency

	// Send a start message to RealTerm
	pc.printf("\fmbed I2C debug tool ready\n\r");
	
	// Scan for I2C devices that reply with ack
	for (i=0; i<=254; i=i+2) {
		if (i2c.read(i, &MasterRX[0], 1) == 0) 
		{
			pc.printf("I2C device detected at address = 0x%02X\n\r", i);
			search++;
		}
	}
	if (search == 0) {
		pc.printf("I2C Slaves NO DETECTED!\n\r");
	} else {
		pc.printf("I2C Slaves %d\n\r",search);
	}
	MasterRX[0] = 0;

	while(1) {
			nRet = i2c.write(addr,MasterTX,sizeof(MasterTX));
			if (nRet == 0) {     // Slave ответил
				orange = 1;
				//green = 0;
			} else {             // Slave не ответил
				orange = 0;
				//green = 1;
			}
			
			memset(MasterRX,0,sizeof(MasterRX));
			strcpy(MasterRX,"ProbaOdnako");
			nRet = i2c.read(addr,MasterRX,4/*sizeof(MasterRX)*/);
			if (nRet == 0) {     // Slave ответил
				green = 1;
				uart.printf("Master RX %d: %s\r\n",nCounter,MasterRX);
			} else {             // Slave не ответил
				green = 0;
			}	
			
			led = 1;
			wait(1.5);
			led = 0;
			wait(1.5);
			nCounter++;
  }			
#else
	int begin = 0, end = 0;
	strcpy(nameDevice,"Slave");
  uart.printf("Uart start %s\r\n",nameDevice);
	
	timer.start();
	slave.frequency(100000); //Set the clock frequency
	slave.address(addr);
	pc.printf("Slave start\r\n");
	
	while(1) {	
		begin = timer.read_us();
		for (i=0;i<1000L;i++) {  // Задержка 1000
			led = 1;
			waitEnable++;
		}
		end = timer.read_us();
		
		memset(SlaveRX,0,sizeof(SlaveRX));
		step = slave.receive();
		switch(step) {
			case I2CSlave::ReadAddressed:   // Master запрашивает ответ от Slave
				strcpy(SlaveTX,"123\0");
				slave.write(SlaveTX,4);
				printf("Slave TX: %s\r\n",SlaveTX);
				uart.printf("Slave TX: %s\r\n",SlaveTX);
				orange = 1;
			break;
			
			case I2CSlave::WriteGeneral:    // Бродкаст
				slave.read(SlaveRX,sizeof(SlaveRX));
				printf("Broadcast RX: %s\r\n",SlaveRX);
				orange = 1;
			break;
			
			case I2CSlave::WriteAddressed: // Master спрашивает текущий Slave
				slave.read(SlaveRX,sizeof(SlaveRX));
				//wait(0.01);
				printf("Slave RX %d: %s\r\n",nCounter,SlaveRX);
				uart.printf("Uart Slave %d: %s\r\n",nCounter,SlaveRX);
				//uart.printf("No critical I2C delay %d us\r\n", end - begin);
				orange = 1;
			break;
			
			case I2CSlave::NoData:
				orange = 0;
			break;
		}		
		nCounter++;
  }			
#endif

}

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Andrey Chepegin

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9 years, 5 months ago.