TCA9543A: Check general understanding of software to use the device

Good catch.  Copy and paste bit me there.   Are these steps generally correct then?

So, I'm working with this device via a board from Mikroe called the I2C Mux 4 Click. I know TI does not support other products, but I have a couple of questions about the TCA9543A, which is on the board.

I can see the TCA9543A at address 0x70; my writing to it using C was successful. I can write 0x01, 0x02, and 0x99, all successfully. (0x99 is just a test value; I realize that's not a valid setting.   )

Once I send a valid channel select value, like 0x01, I do not see the load cell at 0x28 as expected.  I do not have INT or RST connected to anything.  Do they have to be?  I have tried tying them high and low, and the result has no difference.

I have directly connected bot the TCA9543A (address 0x70) and the load cell (address 0x28) to the I2C bus and I can read both of them successfully so I know that the load cell works and the wiring is good to the load cell.

Here is my C code in case it's helpful.

// Basic & generic includes
	
	#include <stdio.h>
	#include <unistd.h>
	#include <string.h>
	#include <stdlib.h>
	#include <fcntl.h>
	
	// includes for time
	#include <time.h>
	#include <sys/time.h>

	// includes for I2C
	
	#include <linux/i2c-dev.h>
	#include <sys/ioctl.h>

	int main()
	{
	    
		  int fd2;
		  int fd1;
		  
		  int args;
		  int x;
		  
		  char buf[3];
	      // clear buffers
			
		  buf[0] = 0x00;
		  buf[1] = 0x00;
		  int result;
		
	// Configure BeagleBone
	
		system("config-pin P9_19 i2c");  // reserved for I2C bus, SDA /dev/i2c-2
    	system("config-pin P9_20 i2c");  // reserved for I2C bus, SCL /dev/i2c-2
		system("config-pin P9_26 i2c");  // reserved for I2C bus, SDA /dev/i2c-1
	    system("config-pin P9_24 i2c");  // reserved for I2C bus, SCL /dev/i2c-1
	
	    usleep(200000); 
	  
	
		if ((fd2 = open("/dev/i2c-2", O_RDWR)) < 0)
		
			{
		    	printf("Failed to open I2C bus 2.");
		    	exit(1);
			}
			
		if (ioctl(fd2, I2C_SLAVE, 0x70) < 0) 
			{
		    	printf("Failed to acquire bus 2 access and/or talk to slave.\n");
		    	exit(1);
			}
		// Repeat reading every second until CTRL-Break to stop or bus / device unreachable
		buf[0]  =0x01;
		buf[1]  =0x01;
		
		result = write(fd2,buf,1);
		
		if (result != 1)
		{
			printf("Unable to write to device on channel.\n");
			exit(-9);
		}
		
		printf("Result of writing to set channel was %d\n",result);
		
		if (ioctl(fd1, I2C_SLAVE, 0x28) < 0) 
			{
		    	printf("Failed to acquire bus 2, mux channel 0 access and/or talk to slave.\n");
		    	exit(2);
			}
		
		while(1) 
			{
				
	        // Drive a reading to start
			
			
			result = read(fd1,buf,1);
			
			if (result !=1) //Assume this will return 0 on success
			{
				printf("Read_MR command on bus failed. Result=%d\n",result);
				exit(1);
			}
			
			// wait
			
			usleep(500000);
			
			if (read(fd1,buf, 2) !=2)
			{
				printf("Read_F2 command on bus failed.\n");
				exit(1);
			}
			else
			{
				printf("Values read from bus are:%2x %2x\n",buf[0]&0x3F,buf[1]);
				
			}
			
			
			}
}

With the load cell connected to channel 0, here is the output.

Result of writing to set channel was 1
Failed to acquire bus 2, mux channel 0 access and/or talk to slave.
make: *** [/var/lib/cloud9/common/Makefile:173: start] Error 2

Hello Walter,

1.Based of the datasheet I would say it is best to tie both the Reset and INT pins to VCC through pull up resistors.

2.Are you seeing something called a NACK bit on the I2C(SDA and SCL) lines when the Load Cell( target device) is not receiving the data from the bus controller?( Would you happen to have any scopeshots of this error occurring? This would be Scope shots  waveforms of the  input signal from the Load Cell (target), and the output signal back to the controller

Here is a good app note that helps debug I2C.

I agree with Clemens comments from above and you, me and clemens can work together to help your system.

Regards,

Kameron

I am not familiar with the details of the /dev/i2c interface. It would be easier to use the tools in the i2c-tools package, e.g., "i2cset 2 0x70 0x01".