I wrote UART echo sample based on ble_app_uart_c for S140/nRF52840-DK.
When nRF52 receive one line on USB/UART, it send same line to USB/UART.
I also write Linux socket sample for keep send/receive one text line to /dev/ttyACM0.
On normal condition, both sample works fine. I can see echoed line on Linux terminal.
But when I press "IF BOOT/RESET" during USB/UART is busy. nRF52 goes unstable condition.
On next open /dev/ttyACM0 is success, but no echo back.
This unstable condition continues until power cycle on nRF52.
Do you know how to prevent becoming unstable condition?
I use nRF52840-DK, PCA10056 1.1.0
Thanks,