How to add uart debug support to BLE DFU

[Andreas]

Hello,

I want to add uart debug support to the BLE DFU bootloader (nRF51822, S120, custom board). Therefor I increased the possible size of the bootloader (start 0x39800, size 0x6400). That works without any problems. Then I added the app_uart.c/app_uart.h module and implemented a uart_open() function:

void uartOpen(void){
uint32_t err_code = NRF_SUCCESS;
app_uart_buffers_t buffers;

	const app_uart_comm_params_t comm_params =  
	{
		RX_PIN_NUMBER, 
		TX_PIN_NUMBER, 
		RTS_PIN_NUMBER, 
		CTS_PIN_NUMBER,
		APP_UART_FLOW_CONTROL_DISABLED,
		false, 
		UART_BAUDRATE_BAUDRATE_Baud38400
	};
         
buffers.rx_buf      = rx_buf;
buffers.rx_buf_size = sizeof (rx_buf);
buffers.tx_buf      = tx_buf;
buffers.tx_buf_size = sizeof (tx_buf);
err_code = app_uart_init(&comm_params, &buffers, uart_error_handle, APP_IRQ_PRIORITY_LOW, &m_uart_uid);
APP_ERROR_CHECK(err_code);}

But when I add a "printf("Bootloader started"); the bootloader hang up. The uartOpen() function seems to work. But it is hard to debug because without printf I can not get any feedback from the system.

What else do I need to add to the bootloader, to get a working uart interface?

Regards, BTProgrammer

[Andreas]

Ok, I have done a little step forward. If I send only one byte via the interface, it is working. So after uartOpen() I do

c='t';app_uart_put(c);

And I get the "t" on my serial terminal. Why does the

void putstring(char * s){
uint32_t err_code;

uint8_t len = strlen((char *) s);
for (uint8_t i = 0; i < len; i++)
{
    err_code = app_uart_put(s[i]);
    APP_ERROR_CHECK(err_code);
}}

not work? Is there a problem with the scheduler?

[Andreas]

OK, I think I solved the problem. I switched from app_uart.c to app_uart_fifo.c. Can anyone explain me, why app_uart_fifo.c does work and app_uart.c does not? Now the complete string is transmitted.

Regards, BTProgrammer

[bjorn-spockeli]

You have to either change your code to

for (uint8_t i = 0; i < len; i++)
{
    while (app_uart_put(s[i]) != NRF_SUCCESS);
}

or use app_uart_fifo.c instead of app_uart.c. Please see this post

[bjorn-spockeli]

See answer to the post I linked to in my answer.

[Andreas]

Thank you Bjørn, now it is much more clear.