LRADC voltage measurement

[joecool]

I try to read out the system voltage levels using LRADC channels.

However, I don't get around with the output values: Channel 6 (VDDIO) gives an output value of about 3640, channel 15 (VDD5V) gives an output value of 2789. What do these values mean, what formula is necessary to get the real voltages?

[igorpadykov]

Hi Joe

i.MX23 LRADC has 12 bits resolution (0-4095 max.), max.1.85V input,

IMX23RM  sect.33.2 Operation, so you can recalculate it

easily.

Best regards

igor

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[joecool]

Oh yes, I didn't expect it to be as simple. ;-) Just wondering if it is a linear measurement, because for die temperature sensing there's also a gamma correction necessary.

Voltage measurement works fine now on pins VDD5V, VDDIO and BATT, but not for VDDM (2.5V). According to the i.MX233 manual channel 4 is bonded to VDDM, but all I can measure from LRADC is something about 3.7 volt. Any idea?

[igorpadykov]

I think you can debug adding printfs

to sources and comparing good LRADC channel with bad.