On Wed, 6 Feb 2013 13:12:54 +0100 (CET), Dag Wieers wrote: > On Wed, 6 Feb 2013, Jean Delvare wrote: > > > The risk is relatively low, but it exists. If you want to make it as > > low as possible, you can start with: > > > > # i2cget 0 0x48 > > > > This will read the presumed internal pointer value from the chip. Write > > down the value for future use. I'll call in $v below. Then try a single > > register read: > > > > # i2cget 0 0x48 $v > > > > If it returns $v again, and $v is neither 0x00 nor 0xff, you better > > leave the chip alone, and cold boot the machine (just in case.) In > > other cases, the chip seem to behave normally and you can go with: > > > > # i2cdump 0 0x48 b > > So here we go: > > root ~ # i2cget 0 0x48 > WARNING! This program can confuse your I2C bus, cause data loss and worse! > I will read from device file /dev/i2c-0, chip address 0x48, current data > address, using read byte. > Continue? [Y/n] > 0x3f > > root ~ # i2cget 0 0x48 0x3f > WARNING! This program can confuse your I2C bus, cause data loss and worse! > I will read from device file /dev/i2c-0, chip address 0x48, data address > 0x3f, using read byte data. > Continue? [Y/n] > Error: Read failed Not good. This can mean one of two things: either the chip has no register 0x3f and it nacks non-existent register read attempts, or it doesn't support SMBus read byte transactions at all. In the latter case, I strongly suggest that you leave the chip alone. As for the former case, there are a few thermal sensor chips which behave like, don't have a register at 0x3f and can use slave address 0x48: DS1621 and similar, DS75, LM73. Please try "i2cget 0 0x48" multiple times and see if it always returns the same value. > root ~ # i2cget 0 0x48 b > Error: Data address invalid! > Usage: i2cget [-f] [-y] I2CBUS CHIP-ADDRESS [DATA-ADDRESS [MODE]] > I2CBUS is an integer or an I2C bus name > ADDRESS is an integer (0x03 - 0x77) > MODE is one of: > b (read byte data, default) > w (read word data) > c (write byte/read byte) > Append p for SMBus PEC The right command here was i2cdump, not i2cget. But given the results of the previous command, it's probably a good thing that you got it wrong. Don't do it (yet.) -- Jean Delvare _______________________________________________ lm-sensors mailing list lm-sensors@xxxxxxxxxxxxxx http://lists.lm-sensors.org/mailman/listinfo/lm-sensors
