APP_UART_FLOW_CONTROL_LOW_POWER missing on SDK11?

[Jim Dattolo]

I have been using this mode to init the app_uart_fifo code on SDK8 for a while now and when moving over to the SDK11 code I was in the app_uart_fifo.c code and it's radically different than stack 8. All of the low power code and gpiote code to catch the CTS transitions are gone. It's still listed in the header file as an option, however no code uses it that I can see.

Did something else change to manage the 1mA continuous current draw issue when using the UART? if it's been solved a different way (e.g. not using the 16mhz clock for the UART) then it would be nice to have it documented. I see nothing in the migration document to say that the UART is being handled any differently with respect to the APIs.

[Christopher]

The UART module of the nRF51 chip still require the HFCLK (see the 8.3 Block resource requirements chapter in the nRF51822 Product Specification v3.1). The UART 1mA continuous current draw is an hardware issue, not a software issue.

From SDK 10, an Hardware Abstraction Layer (HAL) and low-level drivers have been added. The UART peripheral code has changed a lot, but the same features are available (for instance the APP_UART_FLOW_CONTROL_LOW_POWER mode). See the UART module documentation.

[Sydney]

I'm in the process of migrating from SDK7 to SDK11 and started realizing all the low power UART code appeared to be missing, even though the documentation for app_uart_flow_control_t clearly says, "Flow control setting, if flow control is used, the system will use low power UART mode, based on CTS signal." This makes it sound like any use of flow control will use the low power, CTL-controlled implementation, but I don't see the code to do that anywhere.