SARADC's conversion clock frequency

jun1 — Mon, 21 Feb 2022 08:02:14 GMT

Thank you very much for your help.

I'm using MKM34Z256VLL7 and I'm having trouble with the SAR-ADC initialization.
The source is shown below.
On line 21, set clockSource to kADC16_ClockSourceAlt2, BUSCLOCK/2 =20.97152MHz/2 =10.48576MHz.
(clockDivider = kADC16_ClockDivider8)
Then, in ADC16_DoAutoCalibration(), kADC16_ChannelConversionDoneFlag does not stand, so it becomes an infinite loop.
Please let me know why clockSource = kADC16_ClockSourceAlt2 is not good.
I read in the datasheet that the ADC CONVERSION CLOCK should be less than 18MHz.

---

void adcInitialize(void)
{
adc16_config_t config;

/*
* config->referenceVoltageSource = kADC16_ReferenceVoltageSourceVref;
* config->clockSource = kADC16_ClockSourceAsynchronousClock;
* config->enableAsynchronousClock = true;
* config->clockDivider = kADC16_ClockDivider8;
* config->resolution = kADC16_ResolutionSE12Bit;
* config->longSampleMode = kADC16_LongSampleDisabled;
* config->enableHighSpeed = false;
* config->enableLowPower = false;
* config->enableContinuousConversion = false;
* config->hardwareAverageMode = kADC16_HardwareAverageDisabled;
*/
ADC16_GetDefaultConfig(&config);

config.referenceVoltageSource = kADC16_ReferenceVoltageSourceValt;

config.clockSource = kADC16_ClockSourceAlt2; // BUSCLOCK/2 =20.97152MHz/2 =10.48576MHz
config.longSampleMode = kADC16_LongSampleCycle24;
config.hardwareAverageMode = kADC16_HardwareAverageCount32;
ADC16_Init(ADC0, &config);

ADC16_EnableHardwareTrigger(ADC0, false);
ADC16_SetHardwareCompareConfig(ADC0, NULL);

if ((status_t)kStatus_Success == ADC16_DoAutoCalibration(ADC0)) {
The following is omitted.

thank you.

Re: SARADC's conversion clock frequency

jingpan — Wed, 23 Feb 2022 05:31:35 GMT

Hi @jun1 ,

Yes, it looks like a hardware problem. The BUSCLK/2 is not really send to ADC. You can get around this issue by using Alt0 and CFG1[ADIV] field.

Regards,

Jing

Re: SARADC's conversion clock frequency

jun1 — Wed, 23 Feb 2022 10:16:42 GMT

I am always very grateful for your help.
Roger that, I'll set it up with busclk.
Thank you very much.
Have a nice day.

topic SARADC's conversion clock frequency in Kinetis Microcontrollers

SARADC's conversion clock frequency

Re: SARADC's conversion clock frequency

Re: SARADC's conversion clock frequency