💬 BC805M (nRF52805) development board integrated with nRF52-DK
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After making some attempts to connect to the nRF52-DK over its "virtual" port using a number of different terminal emulators, I'm beginning to doubt whether the nRF52-DK actually does support UART hardware flow control with even the nRF52832 that's built into it. I'm having no success with getting hardware flow control to work, but I don't know whether it's user error or just reality for the nRF52-DK. There is this: https://infocenter.nordicsemi.com/index.jsp?topic=%2Fug_nrf52832_dk%2FUG%2Fnrf52_DK%2Fvir_com_port.html which on the one hand gives all the pinouts for TXO RXI CTS and RTS, and seems to imply that there's hardware flow control. But then it seems to contradict that by saying "Note: The mbed OB interface does not support HWFC through the virtual com port." It contradicts because, as far as I can tell, the firmware interface on the nRF52-DK is based on mbed. Maybe it wasn't always so? When I look for firmware to download from Nordic, I only see mbed firmware for the nRF52-DK.
Anyone happen to know?
I have a ticket into Nordic to inquire, but who knows how long it will take to get a satisfactory answer, if ever. Meanwhile, I may have to redesign this PCB to account for either possibility. Hence, the project is on-hold until I get answers.
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Well, I was able to artificially raise the CTS line, which is active low, and halt the transmissions, so I don't think the problem is with the UARTE on the nRF52x. Rather, I think the problem may be with how virtual com ports are handled on PC's, and maybe they aren't configured to properly use RTS and CTS for flow control. At any rate, I was able to crank the UARTE transmission speed all the way up to 941176 baud, and at that speed it takes only a very small artificial delay (around 300usec) after each transmitted string to avoid problems, so I'm just going to do that and move on rather than chase down how to get perfect RTS/CTS working on a PC's virtual com port. So, for that reason, this PCB project will still have value when its finished by keeping the "wiring" all within a single PCB rather than strewn about externally with a rat's nest of actual wires.
