AM2632: Generation of resolver's excitation

Orazio Taglialatela Scafati

Part Number: AM2632

Hi,

we are implementing a software resolver, employing a 10kHz sine wave, synthesized using DAC via EDMA and a samples' table in RAM (we have referred to the dac_sine_dma example in the TI SDK). We need to also use the EDMA to communicate via QSPI with an external flash. This interacts with the sine wave generator, producing a glitch on the output like the one shown in the picture.

Is there a way to continously geneate a sine wave whilst using EDMA for other purposes?

Thanks in advance.

1 month ago

0 Fleenor 1 month ago

TI__Genius 15712 points

Hello Orazio,

I am contacting our EDMA expert to see what might be done here. One idea might be to allow the CPU to handle the QSPI communication or allow the CPU to handle the DAC communication while EDMA is busy handling QSPI interface.

Best Regards,

Zackary Fleenor

0 Aakash Kedia 18 days ago in reply to Fleenor

TI__Mastermind 24614 points

Hi Orazio Taglialatela Scafati,

Are you sharing the eDMA channels between DAC and QSPI interface ?

Best Regards,
Aakash

0 Orazio Taglialatela Scafati 17 days ago in reply to Aakash Kedia

Prodigy 10 points

Hi Aakash Kedia,

we are using two different channels: 0 for QSPI, 1 for DAC. These are configured at startup using the EDMA_allocDmaChannel() function.

Best Regards.

Orazio

0 Orazio Taglialatela Scafati 17 days ago in reply to Fleenor

Prodigy 10 points

Hi Fleenor,

thank you for your reply.

You have suggested to switching to a manual approach to periodically load the DAC as soon as a QSPI transaction is triggered. In order to achieve that, I guess we'd need to know what register to access to determine the sample that has been last transferred via eDMA. We couldn't find any suitable information on that regard.

Also, something that is not clear to us is that eDMA architecture comprises 2 TPTCs that, according to the datasheet, generate concurrent traffic on the L3_MAIN interconnect. Incidentally, it looks like the EDMA_TC_* registers are not used anywhere within the SDK, although the cslr_tptc.h file is included from edma.h.

Any support/clarification is greatly appreciated.

Thank you.

Best regards.

Orazio.

0 Fleenor 17 days ago in reply to Orazio Taglialatela Scafati

TI__Genius 15712 points

Hello Orazio,

I will let Aakash provide additional feedback regarding EDMA usage, a quick check of the EDMA registers and my initial thought is that one of the EDMA_TPTC_TCSTAT register bitfields can you provide you with a status of the active transfer. I am not sure about determining the last ADC sample completed but we will look into this further.