(24-Jan-2023, 11:34 AM)SnowLeopardFPV Wrote: You probably have the wrong COM Port selected or something else is holding the required COM port open (such as Betaflight Configurator). Make sure you have any programs shut down that access COM ports and make sure you are selecting the same COM port in the ExpressLRS Configurator that your FC is actually connected to. You select that in the "Manual serial device selection" box right at the bottom above the Build and Flash buttons.

I originally tried it by powering up the Rx and connecting to com 5, which is what pulls up in Betaflight when I connect to it. Made sure nothing was using that port, but would then get an error, 
"WARNING: Pre-connection option "no_reset" was selected. Connection may fail if the chip is not in bootloader or flasher stub mode.
Connecting......................................

A fatal error occurred: Failed to connect to ESP8266: No serial data received."

Afterwards, I tried to power it in boot loader but holding the button on the Rx when applying power. When doing this method, Com 5 does not populate and I can only attempt using com1. That is when I receive the Baud rate error. This is most likely an error on my part but I haven't been able to find a resolution as of yet.

Your best bet is probably to jump on the ExpressLRS Discord server and post your flashing issue there. One of the ELRS devs should then chime in and try to help you out. Getting assistance from a dev who knows the inner workings of the ELRS code base should yield a quicker resolution. If you do find out the reason for that baud rate error, can you please post the answer back here for the benefit of others who may run into the same issue.

The link below will get you onto the ExpressLRS Discord server...

https://discord.com/invite/dS6ReFY

(24-Jan-2023, 11:34 AM)SnowLeopardFPV Wrote: You probably have the wrong COM Port selected or something else is holding the required COM port open (such as Betaflight Configurator). Make sure you have any programs shut down that access COM ports and make sure you are selecting the same COM port in the ExpressLRS Configurator that your FC is actually connected to. You select that in the "Manual serial device selection" box right at the bottom above the Build and Flash buttons.

After about 4 hours in discord speaking with Deadbyte, it appears that you were correct for one of the issues. Long story short, we got the FC and Rx talking to another again and were able to flash the Rx. All in working order now. I can't recommend that discord channel enough. Deadbyte was extremely patient and inciteful. Thank you all for your assistance and recommendations!

That's good news

I can see that the root cause of your issue was that the ExpressLRS receiver was configured in Betaflight on the wrong UART (UART2 instead of UART3). Also, for reference, you could have left the SBUS wire from the O3 Air Unit connected to the FC because the socket on the FC that the O3 Air Unit plug goes into has a pin for the SBUS wire which goes to UART2 while your ExpressLRS receiver is wired to UART3. As long as you only have one receiver connected to a single UART and the "Serial RX" enabled for just one of the UARTs (in your case UART3 for the ELRS receiver) then any receiver connected to a different UART just gets ignored by Betaflight.