RE: SPI manager queue limitations

Jakub Rzeszutko — Thu, 27 Apr 2017 18:22:00 GMT

Hi Daniel,

Your first solution will not work as you expect. You are passing to function nrf_spi_mngr_schedule address of variable: command_trans. Unfortunately this variable is on stack and will be not valid as soon as you leave send_data_async function. Please try solution proposed by Petter and add static keyword to variables: command_trans and packet .

RE: SPI manager queue limitations

Petter Myhre — Wed, 26 Apr 2017 13:56:02 GMT

What if you make them static? Like here?

RE: SPI manager queue limitations

Daniel Sullivan — Wed, 26 Apr 2017 12:20:40 GMT

WARNING HORRIBLE TEMPORARY SOLUTION WARNING

Just to get this working in the meantime, since 8 byte transfers seem to work with no trouble, I've written a small routine to break larger packets into 8 byte transfers which are then given to the transaction as an array for queueing. It doesn't look as nice on the logic analyser, but as far as I understand SPI, breaking strings is allowed in this manner as long as the bits are still clocked out the same.

void send_data_async(uint8_t * data, size_t len, uint8_t * handler) {
// Number of packets
uint8_t no_pkts = (len + 7) / 8;

// Packet definition
nrf_spi_mngr_transfer_t packet[no_pkts];

uint8_t progress = 0;
for (uint8_t i = 0; i < no_pkts; ++i) {
	uint8_t send_len;
	if ((len - progress) < 8 ) {
		send_len = len - progress;
	} else {
		send_len = 8;
	}
	
packet[i].p_tx_data = (uint8_t const *) data + progress;
packet[i].tx_length = (uint8_t)        send_len;
	packet[i].p_rx_data = (uint8_t *)      NULL;
packet[i].rx_length = (uint8_t)        0;

	progress = progress + 8;
}

// Transaction	
nrf_spi_mngr_transaction_t data_trans = {
					.begin_callback      = start_data_callback,
        .end_callback        = finish_data_callback,
        .p_user_data         = NULL,
        .p_transfers         = packet,
        .number_of_transfers = no_pkts,
        .p_required_spi_cfg  = NULL
};

// Queue
APP_ERROR_CHECK(nrf_spi_mngr_schedule(&m_nrf_spi_mngr, &data_trans));

}

DISCLAIMER: I am not originally a C programmer. They are probably MUCH better ways to do this. If anyone wants to offer any suggestions, or if anyone from Nordic has a clue why this is happening in the first place, it would be very much appreciated!