Trouble receiving UART buffer

[assafi]

Hi,

Im trying to use the NRF51DK evaluation board as a data channel between another MCU and the PCA_10031 bluetooth dongle. Im not using softdevice.

My implementation is based on the radio receiver and transmitter example in the SDK with minor changes.

The setup is working great when the MCU is sending one or two data bytes at low rate, but when there is a ~4 byte buffer, only the first three bytes transferd to the NRF. for example, when the MCU sending the next buffer: ['a','b','c','d','e'] I only see the first three characters.

Currently, the baudrate is 115200 but I have tried lower rates and had exactly the same results. The main loop is:

while(true)
{
	while(app_uart_get(&data) != NRF_SUCCESS){}
	packet = data;
	send_packet();
}

What am I missing here?

Thanks

[Hung Bui]

@assafi: Which app_uart did you use, app_uart or app_uart_fifo? Have you made sure you set the UART_RX_BUF_SIZE (when calling APP_UART_FIFO_INIT) big enough ?

You should test just receiving UART first, comment out the part to send data via BLE.

[assafi]

thanks for your answer. I used app_uart_fifo. The UART_RX_BUF_SIZE is set to 256. The transmitter and reciver have been tested to the rate im expecting from the UART without any problems. Im sure that the bottleneck is the UART.

[Hung Bui]

Could you explain a little bit more on "The transmitter and receiver have been tested to the rate im expecting from the UART without any problems" ? If you only test UART communication between your MCU and the nRF51, what is the result ?

Did you use Hardware flow control ? Have you tried to monitor the UART pins using a logic analyzer ?

[assafi]

Thanks again for your reply. I'm afraid the transmitter and receiver are not relevant to my problem. Let me describe it diffrently: Another MCU is connected to the NRF via UART. The MCU is sending 1-byte each time, with small delay between each transmission. The NRF suppose the cache these bytes and send them to the computer via UART.

while(true)
{
while(app_uart_get(&data) != NRF_SUCCESS){}
app_uart_put(data);
}

The problem is that i can see only the first 3-4 bytes in each transmission cycle (out of 15). When i connect the MCU UART to the computer with FTDI cable, I can see all the data.

Im not using Hardware flow control.

[Hung Bui]

Hi Assafi,

Could you confirm you see the same issue when testing with the UART example in our SDK ? It's located at \examples\peripheral\uart. Could you test the PCA10031 UART communication with PC also ? Have you tried to monitor the UART pins ?