topic Re: LPC802 ADC self calibration in LPC Microcontrollers

LPC802 ADC self calibration

fabx4 — Mon, 30 May 2022 11:43:40 GMT

Hi,

We are beginning to work with LPC802 to replace a former design.

We use the integrated ADC and are wondering about the "Hardware self-calibration" evoked in the AN13102: How to Get Best ADC Accuracy for LPC800.

In this AN, it is written "For detailed usage, see LPC800 UM." but there is nothing on this subject in the user manual (UM11045).

There is an example in LPC802-EX-CODE-MCUXPRESSO bundle but again, there is no trace in the user manual and bit corresponding to ADC_CALMODE is stated as reserved in the UM11045.

Does Hardware self-calibration is still available?

Re: LPC802 ADC self calibration

CarlosGarabito — Wed, 01 Jun 2022 16:21:14 GMT

Hi @fabx4, yes, is still available, a self-calibration is a mechanism which adjusts the internal sampling capacitor banks aiming to compensate for capacitance variations that come out of the factory for each IC unit. It is mandatory for the user to launch the self-calibration of the ADC after each Power On Reset to obtain the ADC accuracy specified in the datasheet

You can see more information about it on the next document https://www.nxp.com/docs/en/application-note/AN13413.pdf witch is for s32 but can apply to LPC80x, so, you can find it on the examples (adc --> lpc_adc_interrupt) on the file fsl_adc.c, approx. on line 346 you find a function ADC_DoSelfCalibration.

Have a good day

Re: LPC802 ADC self calibration

fabx4 — Tue, 07 Jun 2022 11:48:58 GMT

Thank you for your answer Carlos.

Re: LPC802 ADC self calibration

emmanuelJJ — Tue, 19 Jul 2022 14:32:38 GMT

Hi carlos,

The field CALMODE is no more mentioned in ADC control register (User manual UM11045)

So, how can we do the auto calibration?

Best regards,

Emmanuel