ZZ-Cat
commented
10 months ago Short answer
No.
TL;DR
- NRF52 chipset has fixed stepped baudrates.
- These baudrates are nowhere close to 416600 or 420000 baudrates for Crossfire or ExpressLRS receivers.
- The NRF52 chipset won't work with TBS Crossfire receivers, because the baudrate would automatically be set far too low.
- ExpressLRS receivers would need to be flashed with the 250000 baudrate that matches what the NRF52 puts out.
- This can catch people out, if they aren't aware of it.
- If people are made aware of this caveat, it's a "Yes, but..." scenario - The kind I prefer to avoid.
Long answer
Not from what I can see in the source code of the NRF52 board support UART driver.
It's a fork of Adafruit's implementation, which uses a set of 'else if' statements to set the physical baud rate of the NRF52's UART to the nearest value that the hardware is capable of, like so:
uint32_t nrfBaudRate;
if (baudrate <= 1200) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud1200;
} else if (baudrate <= 2400) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud2400;
} else if (baudrate <= 4800) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud4800;
} else if (baudrate <= 9600) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud9600;
} else if (baudrate <= 14400) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud14400;
} else if (baudrate <= 19200) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud19200;
} else if (baudrate <= 28800) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud28800;
} else if (baudrate <= 31250) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud31250;
} else if (baudrate <= 38400) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud38400;
} else if (baudrate <= 56000) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud56000;
} else if (baudrate <= 57600) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud57600;
} else if (baudrate <= 76800) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud76800;
} else if (baudrate <= 115200) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud115200;
} else if (baudrate <= 230400) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud230400;
} else if (baudrate <= 250000) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud250000;
} else if (baudrate <= 460800) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud460800;
} else if (baudrate <= 921600) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud921600;
} else {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud1M;
}When you set the baudrate on an NRF52, the number you pick is not a guarantee that it will be set to your specified value.
EG if you tried to set the baudrate to 420000 or 416600, the NRF52 will automatically set the baudrate to 250000.
What this means is you can't set custom granular baud rates in the NRF52 like you can with all of the other chipsets in the Compatibility Table.
It is this reason alone that I did not initially add NRF52 support, because I view it as a limiting factor and a hidden caveat that renders CRSF for Arduino practically unusable with half of what my library is intended to be compatible with.
I understand that TBS Crossfire receivers use a fixed UART baudrate of 416600, of which would be impossible to set on the NRF52. If you tried, the closest you will have on your NRF52 is 250000 and you will have garbled data, and no matter what you do, it simply won't work.
In ExpressLRS' case, you would need to go into ExpressLRS Configurator and flash your receiver with your custom baudrate to match the limited choice in baudrates that the NRF52 chipset has provided. In this case, it would have to be 250000
I can see this would trip a lot of people up, if thar not made aware of it.
Even if people are made aware of it, the actual NRF52 support would look more like "NRF52 but... [here's a list of hidden caveats that render CRSF for Arduino unusable with all of TBS Crossfire's receivers and partially unusable with ExpressLRS receivers unless you do x, y, and z]" and I prefer to avoid that scenario.
I don't even like the fact that Nordic have provided a chipset with fixed baudrates like this, which means that you're stuck with whatever values they give you and nothing else. Because "too bad if the device you're using has an obscure baudrate that we don't recognise". :woman_facepalming:
I disagree with approaches like this, because I view it as an unnecessary limitation from a developer's perspective.
Additional
I already tried to implement support for NRF52 chipsets as early as version 0.1.0, and that's how I found out about these limitations.
It irritated me that much, that I basically hit "f-- it"; I never published the branch, I discarded the changes I made, deleted the branch, and declared that I avoid NRF52 support like the plague.
If it's anything other than a definite "yes", it's a "no".
kingfisher09
Minimum requirements
What development board would you like me to add?
Hi, I'm trying to use a Seeed Studio XIAO nRF52840 with this library.
As far as I can tell it conforms to the requirements (I think it uses a Cortex M4 though I'm not quite clear on the specifics).
Could you add this functionality?