RTOS/EK-TM4C1294XL: Most elegant way to sample >8 ADC inputs with one trigger

PirateLeChuck

Tool/software: TI-RTOS

Hi,

for my project I need to read 12 analog values back-to-back. What is the most elegant way, as the largest sequence only samples 8 inputs?

Also I need the values to be stored in memory by the DMA, so that close to no CPU time is consumed at all.

Best regards

over 8 years ago

0 Charles Tsai over 8 years ago

TI__Guru**** 191886 points

Hi,
I will suggest you use two sample sequencers (i.e. SS0 and SSI) for a total of 12 channels. In the uDMA you will need to separately set up two DMA channels for SS0 and SS1.

0 PirateLeChuck over 8 years ago in reply to Charles Tsai

Intellectual 380 points

So I would trigger both sequences with the same trigger and just use the ADC_CTL_END only for the last conversion of the second sequencer? Or do I need it for both?

Best regards

0 Charles Tsai over 8 years ago in reply to PirateLeChuck

TI__Guru**** 191886 points

Hi,
You will need to do for both since there are two independent DMA channels for the two sample sequencers. If you only generate DMA request based on the ADC_CTL_END of the second sample sequencer then only the 2nd DMA channel will transfer. The first channel corresponding to the first sample sequencer never received the DMA request.

0 PirateLeChuck over 8 years ago in reply to Charles Tsai

Intellectual 380 points

I solved the problem by redefining the sequence 0 inputs in every HWI. At 1KHz trigger frequency the period is sufficient.

Best regards and thanks for the help!

0 Charles Tsai over 8 years ago in reply to PirateLeChuck

TI__Guru**** 191886 points

Hi,
That will work too but at the expense of some CPU bandwidth. It is your choice.

0 Danny F over 8 years ago

Genius 3850 points

"Most elegant way to sample >8 ADC inputs with one trigger"

the answer is really easy:

0. find someone to do it for you.

1. find a mcu with >8 ADC modules that can be triggered by one signal;

2. find a mcu that can trigger >8 external ADC modules;

3. find >8 mcu with > 1+ ADC modules trigger them individually;

4. find a mcu with > 8 ADC sampling sequence that can be triggered by one signal;

5. give up.

0 PirateLeChuck over 8 years ago in reply to Danny F

Intellectual 380 points

Given that "easy" answer 0 is a joke and that the title is "RTOS/EK-TM4C1294XL: Most elegant way to sample >8 ADC inputs with one trigger", I do not see where your answer contributes to the solution of my problem.

But thanks anyway.

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RTOS/EK-TM4C1294XL: Most elegant way to sample >8 ADC inputs with one trigger