LPC4370 HSADC external VIN_NEG

colinstephant — Tue, 19 Jul 2016 11:50:12 GMT

Hi,

I'm using a LPC4370 HSADC wich is working good with internal DC VIN_NEG reference.

Now I want to use the external reference wich is at 360mV on the board, but as soon as I execute Chip_HSADC_EnablePower(LPC_ADCHS) the VIN_NEG pin outputs 500mV.

Here is the code that we execute :

setupClock(frequency); // Configure clock for measure.

Chip_HSADC_Init(LPC_ADCHS); // Initialize HSADC.

Chip_HSADC_DisablePowerDownMode(LPC_ADCHS);

Chip_HSADC_SetupFIFO(LPC_ADCHS, FIFO_INT_SIZE, PACKED_FIFO); // Configure FIFO.

// Select negative as external reference, Positive as external.

Chip_HSADC_SetACDCBias(LPC_ADCHS, currentChannel, HSADC_CHANNEL_NODCBIAS, HSADC_CHANNEL_NODCBIAS);

for(i = 0; i < 1;i++)

{

Chip_HSADC_SetActiveDescriptor(LPC_ADCHS,0,i); // Activate descriptor table 0 with 0<ID<8.

Chip_HSADC_SetupDescEntry(LPC_ADCHS, 0, i,0);

}

// External trigger only, on falling edge, 0x90 recovery clocks, add channel IF to FIFO entry

Chip_HSADC_ConfigureTrigger(LPC_ADCHS, HSADC_CONFIG_TRIGGER_EXT,

HSADC_CONFIG_TRIGGER_RISEEXT,

HSADC_CONFIG_TRIGGER_NOEXTSYNC,HSADC_CHANNEL_ID_EN_ADD, 0x90);

// Edge detection enabled/Synchronization/No pulse

LPC_GIMA->ADCHS_TRIGGER_IN = (1 << 1 | 1 << 2 | 0 << 3 );

// Only one PWM used as trigger source.

LPC_GIMA->ADCHS_TRIGGER_IN |= 7 << 4; // CTOUT_8

Chip_HSADC_SetupDescEntry(LPC_ADCHS,0, 0, (HSADC_DESC_CH(currentChannel) |

HSADC_DESC_BRANCH_FIRST | HSADC_DESC_MATCH(1)| HSADC_DESC_THRESH_NONE |HSADC_DESC_RESET_TIMER ));

Chip_HSADC_SetPowerSpeed(LPC_ADCHS,true);

Chip_HSADC_EnablePower(LPC_ADCHS);

Chip_HSADC_DisablePowerDownMode(LPC_ADCHS);

Any idea of what's happening ?

Re: LPC4370 HSADC external VIN_NEG

soledad — Fri, 02 Sep 2016 23:49:34 GMT

Hi,

Could you please try using the following configuration?

Chip_HSADC_SetACDCBias(LPC_ADCHS, 0, HSADC_CHANNEL_DCBIAS, HSADC_CHANNEL_NODCBIAS);

Please let me know if this helps.
Have a great day,
Sol

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