Re: Help needed

[Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>]

Hi Tamas,

On Thu, 27 Nov 2008 21:33:36 +0100, Dajka Tamás wrote:
> Hi all,
> 
> I’m trying to use a Texas Instruments TMP175 temprature sensor on an AT91RM9200 system ( i2c-gpio).
> 
> The code (part of it):
> 
> //global vars
> int i2c_handler;
> 
> int main( int argc, char *argv[] ) {
>     int i=0;
>     int value=0;
>     int adapter_nr;
>     int err;
>     int funcs;
>     char buf[8];
> 
>     //we don't have to initialize the I2C, since it's done by the driver
> 
>     //opening the device
>     printf("Opening /dev/i2c\n");
>     if ( ( err = ( i2c_handler = open("/dev/i2c-0",O_RDWR) ) ) < 0 ) {
>         printf("Error opening /dev/i2c-0! Exiting (%d - %s).\n",err,strerror(errno));
>         exit(1);
>     }
> 
>     // check for req funcs
>     printf("Getting available IOCTLs\n");
>     // get funcs list
>     if((err = ioctl(i2c_handler, I2C_FUNCS, &funcs) < 0)) {
>         printf( "Error eeprom_open: %s\n", strerror(err));
>         exit(1);
>     }
>     CHECK_I2C_FUNC( funcs, I2C_FUNC_SMBUS_READ_BYTE );
>     CHECK_I2C_FUNC( funcs, I2C_FUNC_SMBUS_WRITE_BYTE );
>     CHECK_I2C_FUNC( funcs, I2C_FUNC_SMBUS_READ_BYTE_DATA );
>     CHECK_I2C_FUNC( funcs, I2C_FUNC_SMBUS_WRITE_BYTE_DATA );
>     CHECK_I2C_FUNC( funcs, I2C_FUNC_SMBUS_READ_WORD_DATA );
>     CHECK_I2C_FUNC( funcs, I2C_FUNC_SMBUS_WRITE_WORD_DATA );
> 
>     printf("Setting slave addr to 0x79\n");
>     if ( ( err = ioctl(i2c_handler,I2C_SLAVE,0x79) ) < 0 ) {
>         printf("Error setting SLAVE address! Exiting (%d).\n",err);
>         exit(1);
>     }
> 
>     value = i2c_smbus_read_byte(i2c_handler);
>     if ( value < 0 )
>         fprintf( stderr, "Failed to read from I2C device: %m\n" );
> 
>     printf("Reading with read\n");
>     if ( read(i2c_handler,buf,1) != 1 ) {
>         printf("Error reading byte! (%s)\n",buf);
>     }
> 
>     printf("Reading with i2c_read\n");
>     if ( ( value = i2c_smbus_read_byte(i2c_handler)) < 0 ) {
>         printf("Error readiny byte! (%d)\n",value);
>     }
> 
>     printf("Trying direct write!\n");
>     buf[0] = 0;
> 
>     if ( write(i2c_handler,buf,1) != 1 ) {
>         printf("Error writing byte! (%s)\n",buf);
>         return -1;
>     }
> 
> The result:
> root@(none):/mnt/tmp175# ./tmp175
> Opening /dev/i2c
> Getting available IOCTLs
> Setting slave addr to 0x79
> Failed to read from I2C device: Operation not permitted
> Reading with read
> Error reading byte! (X†)
> Reading with i2c_read
> Error readiny byte! (-1)
> Trying direct write!
> Error writing byte! ()
> 
> The ’dmesg’ output, since debug messages are turned on:
> i2c-adapter i2c-0: ioctl, cmd=0x705, arg=0xbee5fde4
> i2c-adapter i2c-0: ioctl, cmd=0x703, arg=0x79
> i2c-adapter i2c-0: ioctl, cmd=0x720, arg=0xbee5fd74
> i2c-adapter i2c-0: master_xfer[0] R, addr=0x79, len=1
> i2c-adapter i2c-0: NAK from device addr 0x79 msg #0
> i2c-dev: i2c-0 reading 1 bytes.
> i2c-adapter i2c-0: master_xfer[0] R, addr=0x79, len=1
> i2c-adapter i2c-0: NAK from device addr 0x79 msg #0
> i2c-adapter i2c-0: ioctl, cmd=0x720, arg=0xbee5fd74
> i2c-adapter i2c-0: master_xfer[0] R, addr=0x79, len=1
> i2c-adapter i2c-0: NAK from device addr 0x79 msg #0
> i2c-dev: i2c-0 writing 1 bytes.
> i2c-adapter i2c-0: master_xfer[0] W, addr=0x79, len=1
> i2c-adapter i2c-0: NAK from device addr 0x79 msg #0
> 
> What’s wrong? Am I just lame, or it’s something with the device?

Double check the slave address. 0x79 isn't a valid address for the
TMP175 according to the datasheet. The highest possible address is 0x77.

-- 
Jean Delvare