LPC55S16-EVK - Temperature sensor reads

embedded_eng_ — Mon, 31 Jan 2022 15:52:41 GMT

Hi all,

I'm using LPC55S16-EVK, and I'm trying to add temperature reads using the built in temperature sensor to my application.

I followed lpcxpresso55s16_lpadc_temperature_measurement example.

Here is my code:

ADC initialization

void init_adc_peripheral() { const lpadc_config_t config = { .enableInDozeMode = true, .conversionAverageMode = kLPADC_ConversionAverage128, .enableAnalogPreliminary = true, .powerUpDelay = 0x80UL, .referenceVoltageSource = ADC_REF, .powerLevelMode = kLPADC_PowerLevelAlt1, .triggerPriorityPolicy = kLPADC_TriggerPriorityPreemptImmediately, .enableConvPause = false, .convPauseDelay = 0UL, .FIFO0Watermark = 0UL, .FIFO1Watermark = 0UL }; POWER_DisablePD(kPDRUNCFG_PD_LDOGPADC); LPADC_Init(ADC_BASE, &config); LPADC_DoOffsetCalibration(ADC_BASE); LPADC_DoAutoCalibration(ADC_BASE); }

Command initialization

void init_adc_command() { const lpadc_conv_command_config_t config = { .sampleChannelMode = kLPADC_SampleChannelSingleEndSideA, .channelNumber = 26, .chainedNextCommandNumber = 0, .enableAutoChannelIncrement = false, .loopCount = 0UL, .hardwareAverageMode = kLPADC_HardwareAverageCount1, .sampleTimeMode = kLPADC_SampleTimeADCK3, .hardwareCompareMode = kLPADC_HardwareCompareDisabled, .hardwareCompareValueHigh = 0UL, .hardwareCompareValueLow = 0UL, .conversionResolutionMode = kLPADC_ConversionResolutionHigh, .enableWaitTrigger = false }; LPADC_SetConvCommandConfig(ADC_BASE, 3, &config); }

Trigger initialization

void init_adc_trigger() { const lpadc_conv_trigger_config_t config = { .targetCommandId = 3, .delayPower = 0, .priority = 0, .channelAFIFOSelect = 0, .channelBFIFOSelect = 0, .enableHardwareTrigger = false }; LPADC_SetConvTriggerConfig(ADC_BASE, 2, &config); }

Function to read temperature sensor:

uint32_t read_adc() { lpadc_conv_result_t config; /*trigger ADC read*/ LPADC_DoSoftwareTrigger(ADC_BASE, 4); /*wait for result*/ while (!LPADC_GetConvResult(ADC_BASE, &config, 0U)){}; /*return data*/ return (uint32_t) config.convValue; } float calculate_temperature() { uint16_t Vbe1 = 0U; uint16_t Vbe8 = 0U; uint32_t convResultShift = 3U; float parameterSlope = DEMO_LPADC_TEMP_PARAMETER_A; float parameterOffset = DEMO_LPADC_TEMP_PARAMETER_B; float parameterAlpha = DEMO_LPADC_TEMP_PARAMETER_ALPHA; float temperature = -273.15f; /* Absolute zero degree as the incorrect return value. */ /* If the temperature sensor need calibration, then read the calibration from the flash. */ uint32_t temperatureSlopeSolidifyValue = (*((volatile uint32_t *)(FSL_FEATURE_FLASH_NMPA_TEMP_SLOPE_ADDRS))); uint32_t temperatureOffsetSolidifyValue = (*((volatile uint32_t *)(FSL_FEATURE_FLASH_NMPA_TEMP_OFFSET_ADDRS))); if (((temperatureSlopeSolidifyValue & 0x1UL) != 0UL) && ((temperatureOffsetSolidifyValue & 0x1UL) != 0UL)) { /* Rejustify slope value and Offset value based on the calibration value. */ parameterSlope = ((float)(uint32_t)(temperatureSlopeSolidifyValue >> 1UL) / 1024.0f); parameterOffset = ((float)(uint32_t)(temperatureOffsetSolidifyValue >> 1UL) / 1024.0f); } Vbe1 = read_adc() >> convResultShift; Vbe8 = read_adc() >> convResultShift; /* Final temperature = A*[alpha*(Vbe8-Vbe1)/(Vbe8 + alpha*(Vbe8-Vbe1))] - B. */ temperature = parameterSlope * (parameterAlpha * ((float)Vbe8 - (float)Vbe1) / ((float)Vbe8 + parameterAlpha * ((float)Vbe8 - (float)Vbe1))) - parameterOffset; return temperature; }

The output I get is around the value: 582.

What I'm doing wrong?

Thanks!

Re: LPC55S16-EVK - Temperature sensor reads

PabloAvalos — Wed, 02 Feb 2022 03:57:58 GMT

Hi @embedded_eng_

Thank you so much for reaching us in our community.

Hope you are well, I would like to ask, what did you change on the SDK example? and which SDK version you are using for the lpadc_temperature_measurement ? Because the conversion for temperature has to be ok.

I will be here to help you, I really appreciate your reply. Please let me know if you have more concerns.

Best Regards.
Pablo Avalos.

Re: LPC55S16-EVK - Temperature sensor reads

embedded_eng_ — Mon, 07 Feb 2022 08:35:00 GMT

Hi @PabloAvalos, thanks for your reply.

I found the problem, I had to use different parameters for the ADC command

const lpadc_conv_command_config_t config = { .sampleChannelMode = kLPADC_SampleChannelDiffBothSide, .channelNumber = 26, .chainedNextCommandNumber = 0, .enableAutoChannelIncrement = false, .loopCount = FSL_FEATURE_LPADC_TEMP_SENS_BUFFER_SIZE - 1U, .hardwareAverageMode = kLPADC_HardwareAverageCount128, .sampleTimeMode = kLPADC_SampleTimeADCK131, .hardwareCompareMode = kLPADC_HardwareCompareDisabled, .hardwareCompareValueHigh = 0UL, .hardwareCompareValueLow = 0UL, .conversionResolutionMode = kLPADC_ConversionResolutionHigh, .enableWaitTrigger = false };

And I had to reset the FIFOs after an ADC read.

LPC MicrocontrollersのトピックRe: LPC55S16-EVK - Temperature sensor reads

LPC55S16-EVK - Temperature sensor reads

Re: LPC55S16-EVK - Temperature sensor reads

Re: LPC55S16-EVK - Temperature sensor reads