Parts of this discussion started on this thread: i-am-trying-to-do-dmx512-protocol
I am using SDK 15.2.0 on an nRF52810. My test board is based off of a Laird BL651 which contains a real (not simulated) nRF52810. I'm using the Segger IDE. My code is based off of the ble_app_uart_pca10040e_s112 example. I made a copy of app_uart_fifo.c and modified to use the nrfx_uarte drivers directly.
I am trying to receive a DMX512 data stream. The DMX controller sends a packet of up to 513 bytes of data at 250KBaud and precedes each packet with a UART BREAK (holds the line low for 90us). In my test case the controller is only sending 65 bytes of data.
I initiate the read using: nrfx_uarte_rx(&app_uart_inst, dmx_rx_buffer, BUF_READ_SIZE ); where BUF_READ_SIZE is 513. Here is my event handler:
static void uart_event_handler(const nrfx_uarte_event_t * p_event, void* p_context)
{
app_uart_evt_t app_uart_event;
uint32_t err_code;
switch (p_event->type)
{
case NRFX_UARTE_EVT_RX_DONE:
{
//never reached??
NRF_LOG_DEBUG("DMX data in:");
NRF_LOG_HEXDUMP_DEBUG(dmx_rx_buffer, p_event->data.rxtx.bytes);
(void)nrfx_uarte_rx(&app_uart_inst, dmx_rx_buffer, BUF_READ_SIZE);
}
break;
case NRFX_UARTE_EVT_ERROR:
app_uart_event.evt_type = APP_UART_COMMUNICATION_ERROR;
app_uart_event.data.error_communication = p_event->data.error.error_mask;
if (app_uart_event.data.error_communication & UARTE_ERRORSRC_BREAK_Msk)
{
size_t amount = nrf_uarte_rx_amount_get(app_uart_inst.p_reg);
NRF_LOG_DEBUG("DMX err: %d %d %d %d", amount, p_event->data.rxtx.bytes, dmx_rx_buffer[1], dmx_rx_buffer[57]);
(void)nrfx_uarte_rx(&app_uart_inst, dmx_rx_buffer, BUF_READ_SIZE);
}
break;
default:
break;
}
}
The good news is I'm capturing the data reliably. The bad news is I can't tell how much data was received. The EVT_RX_DONE handler never gets called unless I reduce BUF_READ_SIZE from 513 to 65 or less. The EVT_ERROR handler is correctly detecting BREAK. I checked it with a scope and the handler gets called consistently 60us after the start of the BREAK which is good. The handler is also seeing a FRAMING error which is expected. It doesn't appear to be missing any of the BREAK events.
Once in the EVT_ERROR handler I can't find the amount of data received before the error occurred.
Also, if I stop the code and check the 513 byte buffer contents, I can see the correct 65 bytes of DMX data, but the 65 bytes of data gets replicated throughout the 513 byte buffer, so I see my data at locations 0-64, but also at 65-129, 130-195, ... .
is there a way to find the number of bytes received before the BREAK and can I stop the data from filling the rest of the buffer after the BREAK is received?
