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
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