i.MX ProcessorsのトピックLRADC sampling rate

LRADC sampling rate

imravi — Fri, 27 Nov 2015 04:16:49 GMT

I have written a driver for capturing data from LRADC 6 channel. I am giving a test input using a signal generator and seeing if the data is captured properly.

Everything is working fine but the best sampling rate i am able to acheive is aroung 100 Khz(capturing 6000 samples in 60 ms). I have set the CYCLE_TIME in HW_LRADC_CTRL3 to 6 Mhz but still the sampling rate. Is it the best i can acheive using LRADC

The board used is IMX 28 and linux kernel is 2.6.31

Re: LRADC sampling rate

igorpadykov — Fri, 27 Nov 2015 07:12:24 GMT

Hi ravi

low sample rate may be caused by delays from operating system,

one can try with os-less (bare metal) test, using i.MX28 OBDS (touch_screen.c)

Lab and Test Software (1)

On-Board Diagnostic Suit for the i.MX28 (REV 1)

http://www.freescale.com/products/arm-processors/i.mx-applications-processors-based-on-arm-cores/i.mx28-processors/i.mx28-evaluation-kit:MCIMX28EVKJ?fpsp=1&tab=Design_Tools_Tab

Best regards

igor

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Re: LRADC sampling rate

imravi — Fri, 27 Nov 2015 09:36:16 GMT

As per the Reference manual of IMX28 with 6Mhz set in the HW_LRADC_CTRL3 register , the sampling speed should be (6*10^6)/13 which comes to 461.5 Khz sampling rate. But the effective rate of sampling is 100 Khz. Can this much of delay be caused by the OS layer.

Re: LRADC sampling rate

igorpadykov — Fri, 27 Nov 2015 10:09:05 GMT

yes, in general such delays may be caused by OS.