Микроконтроллеры

Вот такой чип используется в этих модулях. csr-bc417-datasheet.pdf

См. страницу 80.

11.5.2 UART Configuration While RESET is Active

The UART interface for BlueCore4-External while the chip is being held in reset is tri-state. This will allow the user to

daisy chain devices onto the physical UART bus. The constraint on this method is that any devices connected to this

bus must tri-state when BlueCore4-External reset is de-asserted and the firmware begins to run.