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LPC1518: Two ADCs on ADC0 - crosstalk

Question asked by juergen.josef@gmx.at on Jan 28, 2020
Latest reply on Feb 6, 2020 by juergen.josef@gmx.at

Hi,
i'm trying to use the ADC0_8 and the ADC0_0 at the same time on a LPC1518.
Both ADCs are initialized with there fixed pins:

Chip_IOCON_PinMuxSet(pIOCON, 0, 8, IOCON_MODE_INACT);
Chip_IOCON_PinMuxSet(pIOCON, 1, 0, IOCON_MODE_INACT);
Chip_SWM_EnableFixedPin(SWM_FIXED_ADC0_8);  // P1_0
Chip_SWM_EnableFixedPin(SWM_FIXED_ADC0_0);  // P0_8
Chip_ADC_Init(LPC_ADC0, 0);
Chip_ADC_SetupSequencer(LPC_ADC0, ADC_SEQB_IDX, (ADC_SEQ_CTRL_CHANSEL(8) | ADC_SEQ_CTRL_MODE_EOS));
Chip_ADC_SetupSequencer(LPC_ADC0, ADC_SEQA_IDX, (ADC_SEQ_CTRL_CHANSEL(0) | ADC_SEQ_CTRL_MODE_EOS));
Chip_ADC_SetTrim(LPC_ADC0, ADC_TRIM_VRANGE_HIGHV);
Chip_ADC_StartCalibration(LPC_ADC0);
while (!(Chip_ADC_IsCalibrationDone(LPC_ADC0))) {}
Chip_ADC_SetDivider(LPC_ADC0, 16);

...setting up interrupts...

 

The input voltage on ADC0_0 directly influence the measurement on the ADC0_8 (voltage on ADC0_0 keeps less than the reference voltage).
This happens as soon i just initilialize the fixed pin on ADC0_0 (without sequencer B...).
Without the activation of the fixed pin, all works properly.

Does i forgot something or is this some known issue?
Best Regards
Jürgen

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