Calibration of INTERNAL_1V1 reference

ATmega328p Controller /w pluggable connectors for 6DIO, ICP, 2ADC
rpu_bus
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Joined: Sun Sep 18, 2016 6:07 pm

Calibration of INTERNAL_1V1 reference

Postby rpu_bus » Fri Dec 15, 2017 12:14 am

[SelfTest] has had a place to put the external AVCC reference for some time.

[SelfTest]: https://github.com/epccs/RPUno/blob/6ef9514f493300c6a71b7909e5678e9f071d0a6e/SelfTest/main.c#L36

After measuring a 10mA current through the 100 Ohm resistor on the PL pin of the ICP1 input the reference can be switched and the same current and resistor can be used to find the [1V1] internal band gap.

[1V1]: https://github.com/epccs/RPUno/blob/6ef9514f493300c6a71b7909e5678e9f071d0a6e/SelfTest/main.c#L235

The references are saved in EEPROM as 32-bit unsigned numbers (uint32_t) having units of microVolts.

This is somewhat accurate at present but I think the external 50 Ohm needs to be replaced by a 49.9 Ohm with 0.1% accuracy and I should use the 17mA current source after removing the 10mA on the next update.

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