[yelrx8]

I plan on swapping out the 433MHz RFM22B modules in the mini Oplink modules for the 915MHz modules.

Can I change the freq range to the 915MHz modules on LibrePilot?
What should the Min & Max channels be, for use of 915MHZ in the US?

Thanks

[hwh]

The firmware is hard coded for the 433 MHz module's settings.  Both it and the GCS oplink tab would have to be modified for the 915 MHz module to work.  I picked up a pair of the 915 modules intending to try converting a pair of oplinks but realistically it's unlikely I'll get around to that project until next Winter.

If you program you could fork the project and modify the firmware and GCS yourself.

edit: Winter came sooner than I thought

[Tomcatt]

I was playing with dRonin and it looks like it may support that freq.  I'd have to get one and install it to find out but looks like your already there.

[hwh]

Yes, dRonin supports all three frequency bands but it hasn't been ported to LP yet.

[TheOtherCliff]

I thought it would "just work", albeit with the setup saying it was 433 when it was really 915.

Why is that R19 pullup on NIRQ required only for 915?

[f5soh]

No
Need some mods and also for frequency display.

[TheOtherCliff]

Thanks.
So it looks like a simple replacement of the 433 module with a 915 module would produce 866mhz.

Why is the pullup needed for 915 but not for 433?

[f5soh]

I don't know about the pullup.

A simple module replacement 433 > 915 simply don't work.
The chip (RF22) still want to tune the frequency output to 430-440Mhz but pll cannot do the job due to the Vco that do not cover the frequency range.

Need to define the band used in our code.

[f5soh]

Looks like the 'pullup' you say refers to something planned at some point to define the module soldered on revo pcb. 430 or 915 module
But for what i see the PC3 input seems not used for this usage in Revo code and Sparky simply do not have this 'pin module selection'.



So i think the solution still in software side and module band defined as a config parameter.

[hwh]

...Why is that R19 pullup on NIRQ required only for 915?

The note on the schematic is misleading, while it's next to R19 it talks about a resistor (R22) that's half way up on the other side of the cpu.  It's too bad they didn't put in optional resistors on two pins, it would have been nice to have a way to tell which of the three possible modules was installed.

All three modules will tune the entire range, they just won't get out.  The difference between them is the filters between the chip and the antenna pin on the module.  They're tuned for the module's frequency range.  If you put a 915 module on an oplink it will tune properly to 433 because that's what the software currently tells it to do.  The signal won't get out because the RF22b's filter tuned for 915 blocks it.

[f5soh]

Sorry, my bad.
Thinking about external Vco.

[TheOtherCliff]

Now I understand, I assumed that there was scaling built in so that e.g. sending a center value to a configuration register would cause the center frequency to be used.  You are saying that the PLL divisor (or whatever is used) covers the whole frequency range of all module types so outputting the divisor for 433mhz on a 915 module still call for 433.