SPI TXD write from flash vector in ISR fail

RE: SPI TXD write from flash vector in ISR fail

Hung Bui — Mon, 08 Jan 2024 14:51:19 GMT

Hi Pablo,

Can you please make a simple code to demonstrate the issue. It looks a bit complex in your spi_master_send_recv_irq() that I don't know where flash_array is used in the code.

If you can make something very simple, (maybe bare metal, without using library) just write one single byte after the first byte is sent it would be easier to investigate.

RE: SPI TXD write from flash vector in ISR fail

pslavkin — Sun, 07 Jan 2024 20:26:21 GMT

Hey, tks for your answer, I've added more code related to the issue. Maybe it helps you to undertand what is happening.

Tks. Pablo

RE: SPI TXD write from flash vector in ISR fail

pslavkin — Fri, 05 Jan 2024 15:09:20 GMT

Hi Hung:

this is the first byte sended outside the ISR when invoke the transfer:

static __INLINE void spi_master_send_initial_bytes(spi_master_instance_t * const p_spi_instance)
{
APP_ERROR_CHECK_BOOL(p_spi_instance != NULL);

p_spi_instance->p_nrf_spi->TXD = ((p_spi_instance->p_tx_buffer != NULL) &&
(p_spi_instance->tx_index < p_spi_instance->tx_length)) ?
p_spi_instance->p_tx_buffer[p_spi_instance->tx_index] :
SPI_DEFAULT_TX_BYTE;
(p_spi_instance->tx_index)++;
}

And this is the ISR (part of) that jumps after the first byte gets out of the register:

static __INLINE void spi_master_send_recv_irq(spi_master_instance_t * const p_spi_instance)
{

uint8_t rx_byte;

p_spi_instance->bytes_count++;
rx_byte = p_spi_instance->p_nrf_spi->RXD;

if ((p_spi_instance->p_rx_buffer != NULL) &&
(p_spi_instance->rx_index < p_spi_instance->rx_length))
{
p_spi_instance->p_rx_buffer[p_spi_instance->rx_index++] = rx_byte;
}

if ((p_spi_instance->tx_index < p_spi_instance->max_length) && (!(p_spi_instance->abort_flag)))

{
 p_spi_instance->p_nrf_spi->TXD = ((p_spi_instance->p_tx_buffer != NULL) && (p_spi_instance->tx_index < p_spi_instance->tx_length)) ? p_spi_instance->p_tx_buffer[p_spi_instance->tx_index] :
SPI_DEFAULT_TX_BYTE);

 (p_spi_instance->tx_index)++;
}

return;
}

Array definitions is like:

char ram_array[100]={"hello world"};

char* flash_array="hello world";

The first byte works fine with two arrays as the ps_spi_instance->p_tx_buffer
The following bytes works fine if I use ram_array but not from flash_array.
Nothing hang, everything works except that the data sended is corrupted/garbage when I use flash_array
If I debug with jtag, step by step, everything works like a charm on any array as input
if I copy the p_tx_buffer[i] to a global ram memory before transfer to TXD, it works like a charm on any array as input
if I copy the p_tx_buffer[i] to a local ram memory before transfer to TXD it doesn't work when using flash_array. But if I add a small delay between copy to local and transfer local to TXD it begins to work

My suspicious is that reading from flash and transfer to the TXD register takes time that is not in consideration, but from ram no

I don't know the version of the SDK, but the copyright header said

RE: SPI TXD write from flash vector in ISR fail

Turbo J — Fri, 05 Jan 2024 14:12:01 GMT

Error is in code not shown.

RE: SPI TXD write from flash vector in ISR fail

Hung Bui — Fri, 05 Jan 2024 14:03:40 GMT

Hi Pabloo,
Could you give some more information about your SDK ? Which SDK you use and which version ?
Please also show us how you define flash_array and ram_array.

I assume you have the same problem if you access the TXD address directly instead of using p_spi_instance->p_nrf_spi->TXD.

When you mentioned "does not work" what exactly you meant ? The value was not correct or the application hang or there were no SPI output ?