Quick check of my SPI code & a few related questions

RE: Quick check of my SPI code & a few related questions

snoopy20 — Thu, 16 Jul 2020 08:07:10 GMT

Can close this one, the other SPI thread I have is more relevant now.

RE: Quick check of my SPI code & a few related questions

Susheel Nuguru — Thu, 16 Jul 2020 06:29:24 GMT

Nothing seems to be configured with SPI CONFIG and FREQUENCY register. I am not sure if the peer is responding anything to these bytes. Can you see if there is any meaninful reception from the peer through the logic analyzer?

RE: Quick check of my SPI code & a few related questions

snoopy20 — Tue, 14 Jul 2020 17:47:16 GMT

I've went back and updated the code to use EVENT_READY which I'd missed.

So far:

1. configure pins and turn on SPI(M) (I'm not using input)

 NRF_GPIO->PIN_CNF[CFG_PIN_GLUE_DAT] = pinDisconnectInputBuffer | (GPIO_PIN_CNF_DIR_Output << GPIO_PIN_CNF_DIR_Pos);
 NRF_GPIO->PIN_CNF[CFG_PIN_GLUE_CLK] = (GPIO_PIN_CNF_DIR_Output << GPIO_PIN_CNF_DIR_Pos);

 NRF_SPIM0->PSEL.SCK = CFG_PIN_GLUE_CLK;
 NRF_SPIM0->PSEL.MOSI = CFG_PIN_GLUE_DAT;
 NRF_SPIM0->PSEL.MISO = SPIM_PSEL_MOSI_CONNECT_Disconnected << SPIM_PSEL_MOSI_CONNECT_Pos;
 NRF_SPIM0->ENABLE = SPIM_ENABLE_ENABLE_Enabled << SPIM_ENABLE_ENABLE_Pos;

2. Fill buffer and wait

  NRF_SPI0->TXD = 'M';
  NRF_SPI0->TXD = 'C';
  while (! NRF_SPI0->EVENTS_READY) {}
  NRF_SPI0->EVENTS_READY = 0;

Unfortunately the EVENTS_READY doesn't reach 1 so I'm stuck.

RE: Quick check of my SPI code & a few related questions

snoopy20 — Tue, 14 Jul 2020 12:30:37 GMT

That's correct I don't want EasyDMA for this operation.

The question now is how to keep the double buffer filled up.

If I write to NRF_SPI0->TXD twice what to check to see that NRF_SPI0->TXD is empty (transfered into double buffer) to keep one step ahead of it emptying?

RE: Quick check of my SPI code & a few related questions

Susheel Nuguru — Tue, 14 Jul 2020 12:00:27 GMT

You seems to be using the SPI functionality with the SPIM0 register context. This is a bit confusing.

If you do not want to use the EasyDMA, then use NRF_SPI0 registers which do not have EVENTS_ENDTX. If you want to use the EasyDMA then I think the generation of EVENTS_ENDTX is dependent on the MAXTX setting. I haven't tried mixing the concept of SPIM and SPI even though they are in the same seriobox instance. So not sure if your code is correct or not.