Displaying Voltage as Temperature?!?

Howdy.

I have a thermistor connected to a voltage sensing port (in0_input) on my ADC chip. I have everything running (i.e, /etc/sensors.conf has the voltage->temperature conversion curve programmed into a 'convert' line and 'sensors' is displaying the correct temperature) but the temperature is being displayed as "+21.0 V". Obviously, I'd like to display "+21.0 C".

Is there any way to force sensors to display the reading as a temperature without rewriting my ADC driver to fake a temperature sensing device (which it isn't)?

Thanks,
Chris

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Short answer is no.

One possibility might be to implement your ADC driver as iio driver and then use the ntc_thermistor driver. That would require OF support in your platform, though, and might make it necessary to add another set of tables to the ntc_thermistor driver if you use a different thermistor.

It might also be possible to tell an iio driver that a specific channel is connected to a thermistor, and ask it to return a temperature instead of a voltage. In that case you could use an iio driver and connect it to iio_hwmon. I don't know enough about iio to know for sure and/or to provide details, though.

A third option would be to enhance libsensors to add support for the functionality you are asking for (ie replace one sensor type with another via configuration file). There is actually a ticket open for that:

	http://www.lm-sensors.org/ticket/2258

Guenter

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Howdy,

I'm working to configure lm_sensors and have notice a few strange issues.

I'm working on a TI 8148 on custom hardware.
Linux 2.6.37
lm_sensors lm_sensors-3.3.4

i2cdetect -l shows the following:

	i2c-2   i2c             OMAP I2C adapter                        I2C adapter
	i2c-4   i2c             OMAP I2C adapter                        I2C adapter

I have two TI ADC128D818 ADCs (I cobbled together my own driver while waiting for support -- I see that someone else requested the same driver last week :-). They are:

	adc128d818-i2c-4-1d
	adc128d818-i2c-4-37

"sensors --bus-list" shows the following:

	bus "i2c-4" "OMAP I2C adapter"

Why bus i2c-2 isn't shown, I don't know. That's likely an issue.

I started using the following sensors.conf:

	chip "adc128d818-i2c-4-1d"
	label in0 "Test"

However, I was told that the "bus was unidentified". I used the following sensors.conf, hoping to fix the problem:

	bus "i2c-4" "OMAP I2C adapter"
	chip "adc128d818-i2c-4-1d"
	label in0 "Test"

However, none in0 was not renamed as expected -- it printed as "in0".

It turns out that sensors_substitute_busses() incorrectly renumbers adc128d818-i2c-4-1d to adc128d818-i2c-2-1d and then can't find the labels. If I use the following sensors.conf (or comment out the call to sensors_substitute_busses()), sensors works as expected:

	chip "adc128d818-i2c-*-1d"
	label in0 "Test"

Am I doing something wrong or is there something strange going on with the bus renaming. What is the point of the bus renaming?

Thanks,
Chris

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Hi Chris,

No it's not. sensors --bus-list only lists the relevant buses - the ones with at least one hwmon chip. There's no chip on i2c-2, so it's not listed.

The problem here is that your i2c bus driver is evil and attributes the same name to two different buses. It should not do that. This is a bug in the i2c-omap driver. It should give each bus a distinct name, for example by including the base I/O address in it.

Yes, this works because you don't actually need a bus statement in your case. It is only needed if the same I2C address is used by the same chip type on two or more I2C buses. In your case the bus type and the I2C address are sufficient to uniquely identify each chip.

As explained in the manual page, the I2C bus numbers are not guaranteed to be stable across reboots, while I2C bus names are. But of course the whole logic assumes unique I2C bus names, and you don't have that on your system at the moment.

Jean Delvare

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Unfortunately it is not the only such driver.

Same output on P2020:

i2c-0   i2c             MPC adapter                             I2C adapter
i2c-1   i2c             MPC adapter                             I2C adapter

And on P5040:

i2c-0   i2c             MPC adapter                             I2C adapter
i2c-1   i2c             MPC adapter                             I2C adapter
i2c-2   i2c             MPC adapter                             I2C adapter
i2c-3   i2c             MPC adapter                             I2C adapter

Question is ... would a patch to fix that be accepted by the i2c maintainers ?

Guenter

I think it would, yes, as long as you explain why it is needed.

Jean Delvare