SPI Slave problem with buffers (nRF51, SDK v10) - Bug in nrf_drv_spis_event_t structure?

[puz_md]

Hello,

I've been working with the SPI Slave on a nRF51-DK for several days. I am using the nRF51-DK (PCA10028), S130 v1.0.0 and SDK v10.0.0. First, I set up a RX and TX buffer of equal size (nrf_drv_spis_buffers_set() is called with same RX and TX buffer lengths). In this scenario, everything seemed to work fine.

After I started to implement my SPI protocol, I wanted to change the TX buffer length so that it represents the actual amount of data to transmit. I expected the driver to send the "overread" character for any additional bytes. The RX buffer length was kept at the actual buffer size. In this scenario, I had a lot of trouble with receiving the expected data. I played arount with switching buffer length parameters in nrf_drv_spis_buffers_set() but in the end, I came to the following conclusion:

In the nrf_drv_spis_event_t structure which is reported to the event handler, rx_amount and tx_amount are switched.

Can anyone confirm this bug? If I use the tx_amount value as the number of received bytes, my current implementation seems to work fine.

Update:

SPIS_Test.zip

Here is a sample code that demonstrates the bug. It is a makefile project with GCC toolchain. see hardware_config.h for SPI pins. You can observe the debug output with the Segger JLink RTT Client (see driver/spis.c, spis_event_handler() ).

The software configures a TX buffer of 2 bytes and a RX buffer of up to 200 bytes. Buffers are cleared to 0 before each transaction. Now, when you use a SPI Master to send for example 8 bytes (data bytes are not 0), you can see the that the correct data has been received (8 data bytes) but rx_amount countains 2. On the other hand, tx_amount contains 8 although we only configured a tx buffer length of 2 bytes. You may switch those values and the debug output shows the correct information.

[puz_md]

I'm not in a hurry as there is an easy workaroung (switching values). I just thought that you might want to fix this bug before the next SDK is released.

Can you please remove the image from your previous comment? Please see my private message for details. Thanks a lot!

[Susheel Nuguru]

Thanks puz, I deleted the comment with the image .. i will update this thread when I have new info.

[Susheel Nuguru]

puz_md,

Thanks for this report,

I did some debug and found that this is a bug in the driver in file nrf_spis.h

__STATIC_INLINE uint8_t nrf_spis_tx_amount_get(NRF_SPIS_Type const * p_spis)
{
    return (uint8_t) p_spis->AMOUNTRX;
}

__STATIC_INLINE uint8_t nrf_spis_rx_amount_get(NRF_SPIS_Type const * p_spis)
{
    return (uint8_t) p_spis->AMOUNTTX;
}

Here you can see clearly that wrong registers are fetched. Correct them to the below.

__STATIC_INLINE uint8_t nrf_spis_tx_amount_get(NRF_SPIS_Type const * p_spis)
{
    return (uint8_t) p_spis->AMOUNTTX;
}

__STATIC_INLINE uint8_t nrf_spis_rx_amount_get(NRF_SPIS_Type const * p_spis)
{
    return (uint8_t) p_spis->AMOUNTRX;
}

I will add this in known bugs in here and register an internal ticket for the team to know about it

[Susheel Nuguru]

My my......this is also a bug in SDK11_aplha ... :(

[puz_md]

I know (sorry for not mentioning SDK11). This is why I reported it ;)