(05-Nov-2021, 03:50 PM)ax3141 Wrote: Isn’t it possible to use SPI and free the UART? I thought SPI based ExpressLRS was possible. You would have to go through Betaflight (or similar) to upgrade it.
Hi ax,
I don't know much about SPI nor how it works. As I thought that I understood, the ELRS
receivers use the TBS Crossfire connection and setup. If this SPI "connection" works, then
why not use it for the external receivers
{and other stuff} as well. Surely, this could be
remapped to some pads...or... the manufacturer provide SPI pads. So, now I am even more
confused
My perception is that it is the F411 processor that is short on available "inputs" such are UARTS.
I don't know how the SPI works, what kind of "interference" it provided, nor how the F411 processor
takes those inputs, nor how it is all combined in the CPU.
If it works without using any UARTS, then you would have 2 sets to use. However, sometimes
even two might be a little short. It all depends on what you want to connect.
I also know that there is soft serial, but you still need pads broken out to use the soft serial and
it still needs to be set up...unless the manufacturer sets up the soft serial, already has it set up in
Betaflight, and provides the appropriate pads. Thing about soft serial is that it is slower than a
hard UART which may, or may not, be problematic.
What I don't understand is why not just use a little better processor, such as the F405, which has
plenty of available UARTS. Is the cost between an F411 and an F405 really that much
.
I suppose one could argue that a tiny whoop or small toothpick really doesn't need extra UARTS.
On the other hand, why not? So, if the mounting format for this FC is "whoop" and you only intend
to build small "park" flyer quads, then I suppose you could just make do with the F411.
Just my opinion, but I have long went with the concept of buying FC boards that I can use in ANY build
from a tiny whoop (or rather 2 inch whoop) through a 5 inch quad. For me a 25.5x25.5 diagonally oriented
whoop board with F405, F7, or greater CPU having an amp rating of at least 35A and plenty of UARTS is
just that...UNIVERSAL. Such boards can be used in any build. That way, I can stock up and be sure that
the board can be used or repurposed for any future build or even from one build to another.
Just a side NOTE:
I have used a lot of HIFIONRC and JHEMCU flight control boards with no problems. So far, none of these
boards have given me any problems. Originally, it was KababFPV that recommended the JHEMCU brand
as being a solid performer and very durable. My experience with them bears this out. I tried the
HIFIONRC brand due to the excellent value. I now have this board in several builds. Again, I have had
NO problems nor issues. While these two "budget" brands might be considered low quality products,
my personal experience with them indicates otherwise. I have never had an issue with any of the FC boards.
Plus, I still crash a lot
{I never have spent much time on my landings}, however, I rarely crash into hard
objects under heavy throttle. On the other hand, if something goes wrong or I have to ditch from altitude,
the drop is over 300 feet.