SPIS ORC register not being used

RE: SPIS ORC register not being used

Stefan Birnir Sverrisson — Thu, 11 Sep 2014 11:45:55 GMT

The bug has been confirmed. It will be reported in future versions of the nRF51822/nRF51422 PAN (product anomaly notification) documents. Workaround is as previously stated.

RE: SPIS ORC register not being used

Peter Myerscough-Jackopson — Mon, 08 Sep 2014 10:01:48 GMT

please can you alter this or comment if after chatting with the SPIS people this needs updating.

RE: SPIS ORC register not being used

Peter Myerscough-Jackopson — Thu, 14 Aug 2014 16:02:50 GMT

Thank you for looking at this. I will convert your previous comment to an answer, and select it once you confirm with the SPIS people when they get back in...

RE: SPIS ORC register not being used

Stefan Birnir Sverrisson — Thu, 14 Aug 2014 10:38:33 GMT

I actually tried to set MAXTX = 1 and MAXTX = 3 and that worked, but after trying MAXTX = 0, I get the same results as you, there is nothing sent out on MISO. According to the reference manual, ORC should be clocked out on MISO if transmitted bytes exceed the value of MAXTX, including when MAXTX = 0. The most knowledgeable people on SPIS are not in office today, I will discuss the issue with them when they are available. Meanwhile I report this as a bug. If the slave has no data to send, I guess the workaround could be to set MAXTX = 1 and write the ORC value manually to the TX buffer.

RE: SPIS ORC register not being used

Peter Myerscough-Jackopson — Wed, 13 Aug 2014 14:03:05 GMT

Hi Stefan,

I have tried the following line:

spi_slave_buffers_set(m_tx_buf, m_rx_buf, 0, sizeof(m_rx_buf));

This transmits the first byte of the m_tx_buf, followed by all 0s. (I am using a logic analyzer to see the lines.)

Alternatively, after removing the NULL pointer detection, in spi_slave_buffers_set(...), I tried this code:

spi_slave_buffers_set(NULL, m_rx_buf, 0, sizeof(m_rx_buf));

This transmits all 0s, and not the ORC byte. I have also tried setting all four bytes of the ORC register to see if the higher bytes are actually being used.

N.B. If I transmit one byte, i.e. spi_slave_buffers_set(m_tx_buf, m_rx_buf, 1, sizeof(m_rx_buf)) the ORC byte is transmitted.

RE: SPIS ORC register not being used

Stefan Birnir Sverrisson — Wed, 13 Aug 2014 09:36:38 GMT

Hi Peter

Are you setting your NRF_SPIS1->MAXTX = 0 in the spi_slave_init function? If so, that does not work because the MAXTX configuration is overwritten when you call spi_slave_buffers_set. To adjust the MAXTX, modify the third parameter when you call spi_slave_buffers_set function. The spi_slave_buffers_set function is called for the first SPI transaction in spi_slave_example_init but for all subsequent SPI transaction in the SPIS handler, i.e. spi_slave_event_handle. So to set MAXTX as e.g. 3, set

err_code = spi_slave_buffers_set(m_tx_buf, m_rx_buf, 3, sizeof(m_rx_buf));
APP_ERROR_CHECK(err_code);