TMS320F28386D: DMA Trriger twice SPI read data

W Z

Expert 2370 points

Part Number: TMS320F28386D
Other Parts Discussed in Thread: ADS7038

TMS320F28386D connect with ADS7038 by SPI (SPI 8 channels ADC slave)

Due to this SPI ADC slave ,one SPI communication cycle only can get one channel ADC data.

We need the two channel ADC data within 11us.(ISR)

So, I have question: Could the below method happen?

In the end of 11us ISR to trriger the DMA by software source, transfer the data to SPI FIFO.

But this DMA shall trigger twice SPI communication cycle.

(Here is the key question, can DMA trigger twice SPI communication cycle)

At the beginning of 11us ISR, to read the SPI FIFO data.

over 2 years ago

0 W Z over 2 years ago

Expert 2370 points

Or is there method to set the times of DMA transfer data to SPI TX FIFO?

0 Manoj Santha Mohan over 2 years ago in reply to W Z

TI__Guru 55700 points

W Z,

Can you please rephrase your question? Does ADS7038 SPI provide multiple ADC channel results on a single SPI communication channel?

In your case, F28386D SPI is the CONTROLLER (master) and ADS7038 is PERIPHERAL (slave). You should expect to receive ADC results on SPISOMI pin.

Please share any timing waveform (or) command structure for me to provide any meaningful feedback.

Regards,

Manoj

0 W Z over 2 years ago in reply to Manoj Santha Mohan

Expert 2370 points

Simplify the qequestion:

Does DMA support burst mode that trggier one time. The DMA can transfer the data to SPI FIFO at fixed interval twice.

As below picture shows. I need one trigger source(I suppose DMA) which can perform two SPI communication cycle to read back the data from SPI slave.

+1 Manoj Santha Mohan over 2 years ago in reply to W Z

TI__Guru 55700 points

W Z,

If you want 2 bursts per trigger. You can set transfer size as 2 and use one-shot mode

Regards,

Manoj

0 W Z over 2 years ago in reply to Manoj Santha Mohan

Expert 2370 points

I had done and it works. I want to set the interval time setting between two burst. For exmaple, transfer the first burst then wait for 2us then transfer the second burst . I do not find this setting.

+1 Manoj Santha Mohan over 2 years ago in reply to W Z

TI__Guru 55700 points

We cannot implement arbitary delay between bursts in ONESHOT mode.

If you looking for have delay, have transfer size as 1 and this way 1st DMA trigger event does 1 burst. Then wait for 2 us and initiate another burst with DMA SW trigger.

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TMS320F28386D: DMA Trriger twice SPI read data