LPC11C24 ADC channels 5-7 not working

lpcware — Wed, 15 Jun 2016 19:40:30 GMT

Content originally posted in LPCWare by over9k on Fri Aug 28 08:29:43 MST 2015
I am writing a program for LPCXpresso LPC11C24 that uses ADC to measure 3 voltages. I want to use ADC channels 2, 3, 7. But channels 0-4 work properly while 5-7 behave in a weird way. Here are the results I get:

Chan | GND | 3,3V | Not Connected
0-4  |  0  | 1023 | ~200
5-7  |  0  | ~5   | 0

And I checked with an oscilloscope, the voltage is really 3,3V there when I measure it, so there is no unexpected drain during measurement. I also have the same problem with one other board, so it's unlikely to be a manufacturing error. I looked at the documentation and there was no hint about why channels 5-7 would be different from 0-4, but maybe I missed something.

Am I doing something wrong? How do I make it work?

Here is my code (I'm using LPCOpen libraries


#include "board.h"

#include <cr_section_macros.h>

#include <string.h>
#include <stdlib.h>
#include <stdio.h>

static ADC_CLOCK_SETUP_T ADCSetup;
Status status;

int adc(char *param1){
uint8_t channel;
uint16_t dataADC = 0;

if(strcmp("2", param1) == 0){
channel = ADC_CH2;
}else if(strcmp("3", param1) == 0){
channel = ADC_CH3;
}else if(strcmp("7", param1) == 0){
channel = ADC_CH7;
}

Chip_ADC_EnableChannel(LPC_ADC, channel, ENABLE);

Chip_ADC_SetStartMode(LPC_ADC, ADC_START_NOW, ADC_TRIGGERMODE_RISING);

/* Waiting for A/D conversion complete or timeout */
for (int i = 0; i < 500000; i++) {
if (Chip_ADC_ReadStatus(LPC_ADC, channel, ADC_DR_DONE_STAT) == SET) {
break;
}
}

status = Chip_ADC_ReadValue(LPC_ADC, channel, &dataADC);

Chip_ADC_EnableChannel(LPC_ADC, channel, DISABLE);

return (int)dataADC;
}

int main(void) {

SystemCoreClockUpdate();
Board_Init();

//Configuring ADC pins.
Chip_IOCON_PinMuxSet(LPC_IOCON, IOCON_PIO1_1, FUNC2); //ADC2
Chip_IOCON_PinMuxSet(LPC_IOCON, IOCON_PIO1_2, FUNC2); //ADC3
Chip_IOCON_PinMuxSet(LPC_IOCON, IOCON_PIO1_11, FUNC2); //ADC7

/* ADC Init */
Chip_ADC_Init(LPC_ADC, &ADCSetup);

int measurement2, measurement3, measurement7;
while(1){
measurement2 = adc("2"); //1023 at 3,3V, around 200 when not connected, 0 when connected to GND.
measurement3 = adc("3"); //1023 at 3,3V, around 200 when not connected, 0 when connected to GND.
measurement7 = adc("7"); //between 4 and 6 at 3,3V, 0 when not connected, 0 when connected to GND.
}//Debug breakpoint here to read the values.

return 0 ;
}

Re: LPC11C24 ADC channels 5-7 not working

lpcware — Wed, 15 Jun 2016 19:40:31 GMT

Content originally posted in LPCWare by R2D2 on Fri Aug 28 09:29:58 MST 2015

Quote: over9k
...but maybe I missed something.

Am I doing something wrong? How do I make it work?

Chip_IOCON_PinMuxSet(LPC_IOCON, IOCON_PIO1_11, [color=#f00]FUNC2[/color]); //ADC7

AD5-7 are FUNC1

PIO1_11 FUNC2 is CT32B1_CAP1 :((

Re: LPC11C24 ADC channels 5-7 not working

lpcware — Wed, 15 Jun 2016 19:40:32 GMT

Content originally posted in LPCWare by over9k on Fri Aug 28 10:01:42 MST 2015
Thank you! You have no idea, how much time I wasted on that. I'll test it on Monday when I get back to work.

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LPC11C24 ADC channels 5-7 not working

Re: LPC11C24 ADC channels 5-7 not working

Re: LPC11C24 ADC channels 5-7 not working