Question

Good day,
I want to read/measure the voltage supply that powers my RUT956 router. It has the MeiG SLM750 modem. I have been able to use the following command from the commandline: gsmctl -A AT+ADCREAD=0. It returns = 773383.

How I should I interpret/scale the returned value to calculate the supply voltage in mv or V?

Many thanks
Francois

Answer 1

Hi,

The modem is not directly powered by the main PSU and the voltage is different than the input voltage.

The voltage here is microvolts, so to translate this reading to proper volts use this formula:

k= 0,0893 in this case

Input V=ADC reading / 1000000 / 0.0893

This would get you around 8.6V, it's not 100% accurate, there is around 0.25V difference

For future refference to anyone that is looking

Voltage divider ratio k for RUT2XX and RUT9XX devices is 0.0893

Voltage divider ratio k of TCR100 is 0.0909.

TRB245 voltage divider coefficient k is 1/11, which is 0.0909

TRB255 voltage divider coefficient k is 4.7/104.7, which his 0.04489

Comments

Hi Paulius

Thank you very much for this. Is there then a way to read/measure the input voltage on the device? Or is it only possible to measure the modem voltage?

Many thanks
Francois

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RUT956 has an analog input, so you could use that to measure the voltage