Creating Two SPI instances for same slave

RE: Creating Two SPI instances for same slave

Thangaraj — Mon, 04 Apr 2016 08:56:49 GMT

Thanks a lot , Ole ... For your quick responses !

RE: Creating Two SPI instances for same slave

Ole Bauck — Mon, 04 Apr 2016 07:34:34 GMT

It will disconnect the pins (write 0xFFFFFFFF to the PSEL registers) of the SPI1 peripheral to allow other peripherals to use the pins without any trouble. See here.

RE: Creating Two SPI instances for same slave

Thangaraj — Mon, 04 Apr 2016 05:59:01 GMT

Can you please explain, what these lines will do ?

NRF_SPI1->PSEL.MISO = (SPI_PSEL_MISO_PSELMISO_Disconnected << SPI_PSEL_MISO_PSELMISO_Pos); NRF_SPI1->PSEL.MOSI = (SPI_PSEL_MOSI_PSELMOSI_Disconnected << SPI_PSEL_MOSI_PSELMOSI_Pos); NRF_SPI1->PSEL.SCK = (SPI_PSEL_SCK_PSELSCK_Disconnected << SPI_PSEL_SCK_PSELSCK_Pos);

RE: Creating Two SPI instances for same slave

Ole Bauck — Fri, 01 Apr 2016 11:35:51 GMT

If they are using the same pins it is no surprise i doesn't work. When uninitializing the SPI instance it will free the pins used, such that the SPIM instance will be able to use them. Try to do this instead of uninit:

NRF_SPI1->PSEL.MISO = (SPI_PSEL_MISO_PSELMISO_Disconnected << SPI_PSEL_MISO_PSELMISO_Pos);
NRF_SPI1->PSEL.MOSI = (SPI_PSEL_MOSI_PSELMOSI_Disconnected << SPI_PSEL_MOSI_PSELMOSI_Pos);
NRF_SPI1->PSEL.SCK = (SPI_PSEL_SCK_PSELSCK_Disconnected << SPI_PSEL_SCK_PSELSCK_Pos);

You will ofcourse have to set them up again (and disconnect the SPIM2 pins) before using SPI1 again.

RE: Creating Two SPI instances for same slave

Thangaraj — Fri, 01 Apr 2016 04:14:15 GMT

Hi, I tried creating two SPI instances SPI1 and SPIM2 for the same slave device connected to pins 11(SCLK), 12(MOSI), 13(MISO), 14(CS), done a 4 byte transaction with slave using SPI1 and it was success followed by 3 seconds delay I tried to do DMA transaction with the same slave but it was not success.

The same code when I start the DMA transaction after I uninit the SPI instance created for CPU transaction then it is fine.

In the above scenario I'm not using the SPI slave (data transaction) at the same time by using both instances. what would be the reason for this behaviour?

RE: Creating Two SPI instances for same slave

Thangaraj — Wed, 30 Mar 2016 12:34:58 GMT

Hi, Our intention is to do both DMA transaction and non-DMA transaction with one Slave device. We may use only one transaction at a time. In that case as you said, wont there be any issues ?

RE: Creating Two SPI instances for same slave

Ole Bauck — Wed, 30 Mar 2016 11:01:09 GMT

Are you going to use the same pins (MISO, MOSI, SCK, CS) for both SPI instances? If so it will most likely not work unless you always makes sure that the two instances doesn't use the pins at the same time. If you are not going to use the same pins, using two SPI instances for the same slave device is just fine.