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.

[Jim Dattolo]

removal of the low power support makes the chip unusable on battery based applications that need the UART. The entire point of the low power mode was to allow apps that could do the non-standard flow control the ability to keep the UART off and save the 1mA continuous draw. By formally removing the support you are forcing your customers to either keep SDK9 running or if they upgrade they need to copy the SDK9 UART code into their app and use that. Hardly a good solution if someone is just starting out with the chip and never was on SDK8 or 9