MKM34Z256VLL7 ADC conversion

davidmalovrh — Thu, 13 Oct 2016 15:27:21 GMT

We are using Kinetis MKM34Z256VLL7 device. AFE is set to software trigger continuous conversion mode. XBAR is used to trigger PDB with AFE COCO and the ADC conversion result is read in AFE callback. After about half a minute conversion results from ADC freezes although the AFE COCO interrupt is still occurring. Code and settings are from example DRM162 - Three Phase Power Meter Reference Design (REV0) from 2015. What could be wrong?

Re: MKM34Z256VLL7 ADC conversion

MarMi — Mon, 17 Oct 2016 06:51:08 GMT

Hello David,

The problem is probably caused by the big phase shift between voltage and current (the calibration value ramcfg.delayX is to big).

You can try change constant in the file “mk32z256_3ph.h”

#define ASD_L1M 0

#define ASD_L1M 4

#define ASD_L1M 8

But the best way should by to use the SW phase shift compensation method. You should by phased PDB, so to directly connect SD to SAR

/* AFE module */

SIM_SelAfePllClk (SIM_MCG_PLL_CLK);

AFE_ChInit (CH0,

AFE_CH_SWTRG_CCM_PGAOFF_CONFIG(DEC_OSR1024),

(0 * SAR_SCT),

PRI_LVL0,

(AFE_CH_CALLBACK)afech0_callback);

AFE_ChInit (CH1,

AFE_CH_SWTRG_CCM_PGAOFF_CONFIG(DEC_OSR1024),

(1 * SAR_SCT),

PRI_LVL0,

(AFE_CH_CALLBACK)afech1_callback);

AFE_ChInit (CH2,

AFE_CH_SWTRG_CCM_PGAOFF_CONFIG(DEC_OSR1024),

(2 * SAR_SCT),

PRI_LVL0,

(AFE_CH_CALLBACK)afech2_callback);

AFE_Init (AFE_MODULE_RJFORMAT_CONFIG(AFE_PLL_CLK, AFE_DIV2, AFE_CLK));

/* ADC module */

ADC_Init (ADC_MODULE_DIV4_16B_HWTRG_IREF_CONFIG,

HWAVG_OFF,

ADC_CH_SE_POLL_CONFIG(ADC_SE0),

ADC_CH_SE_POLL_CONFIG(ADC_SE1),

ADC_CH_SE_POLL_CONFIG(ADC_SE2),

ADC_CH_DISABLE_CONFIG,

PRI_LVL0,

(ADC_CALLBACK)NULL);

/* SD to SAR connection */

XBAR_Path (XBAR_AFE0COC, XBAR_ADCTRGCHA); // SAR start triger

XBAR_Path (XBAR_AFE1COC, XBAR_ADCTRGCHB); // SAR start triger

XBAR_Path (XBAR_AFE2COC, XBAR_ADCTRGCHC); // SAR start triger

And calculate phase shift by the library function

rotation = METERLIB3PH_ProcSamples(&mlib,u24_samplePh1,i24_samplePh1,u24_samplePh2,

i24_samplePh2,u24_samplePh3,i24_samplePh3,shift);

where the “shift” is defined

static frac16 shift[] = { METERLIB_DEG2SH(-5.5, 50.0),

METERLIB_DEG2SH(-5.5, 50.0),

METERLIB_DEG2SH(-5.5, 50.0) };

Where “-5.5” is angle for compensation and “50” is nominal line frequency….

Regards Lukas

Re: MKM34Z256VLL7 ADC conversion

xiangjun_rong — Mon, 17 Oct 2016 09:26:42 GMT

Hi, David,

I suppose that the PDB module has error, As you know that the example uses two ADC converter:SD-AFE and SAR ADC, can you enter the SAR-ADC interrupt? if you can not, pls check the PDB0_CHnS, I suppose that the PDB has error, PDB can not trigger SAR ADC.

If it is PDB error, you can consider the solution as martin said.

Hope it can help you.

Xiangjun rong

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