nRF51822 SPI master

RE: nRF51822 SPI master

Dmitry — Fri, 16 Oct 2015 13:15:51 GMT

Hi,

Thanks to all for the answers.

So far I couldn't resolve the issue but I've found another library which I used to implement all I need (erasing flash, reading and writing the data). The library is attached: spi_master.zip

If someone is going to use the library do the following:

Change pins definition in header file (CLK, MISO, MOSI, CS) according to your schematic design.
Call spi_master_init from main file or from the library which is based on the library I've attached. For example, if SPI0 is used in the mode 0 with MSB first call the function:

spi_base_address = spi_master_init(SPI0, SPI_MODE0, (bool)0);
Use function spi_master_tx_rx to send/receive data. For example, in my case mentioned in the first post the code

tx_data[0] = 0x9F;

spi_master_tx_rx(spi_base_address, 4, (const uint8_t *)tx_data, rx_data);

will return SPI flash ID in the rx_data array.

Hope this helps.

Regards, Dmitry.

RE: nRF51822 SPI master

MartinBL — Mon, 12 Oct 2015 12:36:50 GMT

Hi. I have experimented for a while now and using your code I see the same behaviour as you do. Although I haven't been able to pinpoint exactly what is happening @Nathan is correct. Calling spi_master_send_recv() consecutively without waiting for the previous transmission to end will fail.

A simple solution that works for me is to set a flag in the spi event handler like this:

void spi_master_event_handler(spi_master_evt_t spi_master_evt)
{
    if(spi_master_evt.evt_type == SPI_MASTER_EVT_TRANSFER_COMPLETED)
        m_transfer_completed = true;
}

and then wait with a while loop for transmission 1 to complete before you start transmission 2:

while(!m_transfer_completed);
m_transfer_completed = false;

It sounds like you have tried to implement something like this though? Do you mind sharing you code?

RE: nRF51822 SPI master

Dmitry — Fri, 09 Oct 2015 05:46:12 GMT

Hi Nathan,

Thanks for the reply.

I added the feature you talk about but I guess the problem lies elsewhere. I've found a mistake but it doesn't solves the problem: when calling

spi_master_send_recv(SPI_MASTER_0, tx_data, 4, rx_data, 1);

I should use value 5 instead 4 because master latches transfer from slave during 5th byte. Accordingly RX buffer should have 5 elements instead 4 in my case.

The issue which is still there is that spi_master_send_recv function changes TX buffer contents to the original value although new value is passed as an argument: in my case if step in the function during second call I observe that tx_data[0] assigned by 0x9F. This occurs when the following instruction has been called:

volatile spi_master_instance_t * p_spi_instance = spi_master_get_instance(
    spi_master_hw_instance);

Any thoughts?

RE: nRF51822 SPI master

Nathan — Thu, 08 Oct 2015 17:55:11 GMT

Dmitry,

The spi_master_send_recv function is non-blocking, it just kicks off the SPI hardware to start the transaction. When the transaction is completed, an interrupt will fire and call the event handler you passed to the spi_master_init function (in your case, spi_master_event_handler). You need to wait for the event hander to be called with the SPI_MASTER_EVT_TRANSFER_COMPLETED event type before calling spi_master_send_recv again with the new data.

Alternatively, you can use the uint32_t return value of spi_master_send_recv to determine when data has been sent successfully. The function will return NRF_SUCCESS if the data was added to the SPI output correctly, or it will return NRF_ERROR_BUSY if a transaction is currently in progress and the data will not be sent.