NRF54 BLE UART PERIPHERAL works only when the debugger is connected

RE: NRF54 BLE UART PERIPHERAL works only when the debugger is connected

Kazi Afroza Sultana — Wed, 14 May 2025 15:05:28 GMT

Added to my previous comment: Can you please show the current device tree overlay file?

RE: NRF54 BLE UART PERIPHERAL works only when the debugger is connected

Kazi Afroza Sultana — Wed, 14 May 2025 15:04:52 GMT

Hello,

Apart from the default pin sets for UART communication on NRF54L15

You Can connect across power domains to dedicated pins on P2. You have to change the overlay file.

Selected pins of P2 can be used for some serial interfaces in the peripheral domain — SPIM, SPIS, and UARTE. This is not the most power-efficient way of connecting these serial interfaces but adds flexibility when designing a circuit board. When setting up the peripheral's PSEL register for cross-domain connections, it must be connected only to the corresponding function listed in the pin assignments table. For example, the peripheral's PSEL.SCK register must use the P2 SCK pin from the pin assignment table. The pin assignments table shows which pins can be configured for cross power-domain connections.

You have to change the device tree accordingly, in the hardware the RX and TX pin should be powered from the default pin; as its mentioned in the previous case ''Connected wires from P1.04/05 -> P2.07/08 on the DK for easier access to the uart console.''. You can also connect P2.07 or P2.08 with external UART or US converter.

You also need to add this kconfig in the prj.conf file

CONFIG_SOC_NRF_FORCE_CONSTLAT=y

RE: NRF54 BLE UART PERIPHERAL works only when the debugger is connected

riad-france — Tue, 29 Apr 2025 07:26:36 GMT

Hi,

I found a similar issue here nRF54L15: UART pinout not working unless connecting the RTT viewer.

This appears to be a temporary workaround :

#include <uart_async_adapter.h>

...

int main(void) {
  NRF_TAD->ENABLE = 1;
  ...
}

It would be interesting to understand why the application require this special mode (Enable debug domain and aquire selected GPIOs).

Do you have any information on the subject ? Thanks

RE: NRF54 BLE UART PERIPHERAL works only when the debugger is connected

riad-france — Thu, 24 Apr 2025 09:33:08 GMT

Hi,

- We kept the default value of 128 for CONFIG_BT_NUS_UART_BUFFER_SIZE, as it is sufficient for our current data transmission needs.

- The baud rate is set to 115200. Below is the full configuration output from stty -F /dev/ttyLP2 -a

speed 115200 baud;stty: /dev/ttyLP2
 line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>; eol2 = <undef>; swtch = <undef>; start = ^Q;
stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0;
-parenb -parodd -cmspar cs8 hupcl -cstopb cread clocal -crtscts
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff -iuclc -ixany -imaxbel -iutf8
opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt echoctl echoke -flusho -extproc

RE: NRF54 BLE UART PERIPHERAL works only when the debugger is connected

Kazi Afroza Sultana — Thu, 24 Apr 2025 09:12:13 GMT

Hello,

What is the buffer size you set for the sample in configuration? If the goal is to transfer large chunks of data, 128-512 bytes would be more appropriate. You can set this in the config file

CONFIG_BT_NUS_UART_BUFFER_SIZE=x

Did you set the baudrate 115200 in the terminal?

RE: NRF54 BLE UART PERIPHERAL works only when the debugger is connected

riad-france — Fri, 18 Apr 2025 07:54:33 GMT

*Full chip reference is nRF54L15-QFAABB2435AB