TODO list

M17 standard:
[*]testing! a lot of testing

TR-9 radio:
[]check doppler effect influence on reception
]design a case
[]remove 5V voltage regulator
]dynamically change the clock, we don’t need to run full 216MHz on idle

M17 repeater:
[]add power envelope control
]finish telemetry website

I’m currently re-drawing the schematics in KiCAD and will incorporate the TODOs. While I’m at it, I would suggest reworking the power supply circuit to include a LiPo charger, buck/boost converter for a stable 7.5V PA voltage and a switching regulator to ~4V with an LDO for 3.3V in series. Does this sound alright?

Yeah, it sounds good. We should also change the connectors for the GPS module and keyboard. They are just a 3-pin goldpins atm.

GPS module will use 5 wires - 5V/RX/TX/PWR_EN/GND. Take a look at Sparkfun GP-735. We would also need the 5V line.
Keyboard is just 3,3V/TX/GND (transmit only).

What error coding scheme are you trying to use? I’m using the libcorrect library to implement convolutional coding (as well as RSV) on QMesh, and the STM32F7 should be powerful enough to support encoding and decoding it in real-time.

Also, do you have any interest in using a LoRa chipset (e.g. the Semtech SX1276 or SX1262) in your design instead of the SI4460? For M17, it should have all of the FSK features that the SI4460 gives you, but also has the option of LoRa modulation if you want to play around with that at some future point in time. Basically, LoRa gives you more receive sensitivity and resistance to narrowband interference vs. FSK. There’s some other quasi-CDMA things you can do with as well.

I could help you port over to a LoRa chipset if you’re interested.

-Dan Fay

libcorrect looks good to me, probably R-S codes. I’m gonna check it out today.
I’m not sure about LoRa, gonna let others comment on that.

I’ve finished re-drawing the schematics in KiCAD with some of the Todos incorporated and a few others added as text! Please let me know what you think :slight_smile:



  1. do we need a power switch? what if we used an encoder with a pushbutton and detect it by the micro?
  2. that GPS module I have mentioned before (Sparkfun GP-735) is supplied by 5V, so It’d be better to find another one, 3,3V-powered it’s 3,1-5,5V
  3. J5 connector is available at
  4. some of Si4463 pins are left floating, but the labels are probably placed correctly
  5. RV1 is an SMT type trim pot
  6. loudness control is done by software (there are 3 variables - for mic gain, speaker volume and “beeps” volume [sound effects])
  7. external PTT/mic/spk - Kenwood standard - aye!
    8.) page 6 - diodes D2/D3 are incorrectly polarized
  8. the mic I used is electret
  9. GPS and keyboard connectors should be low-profile
  10. GPS with an IMU - great idea, are there any?


  1. Exactly, I was thinking about something like that. Either encoder with push button or pot with switch.
    2 + 11) The ublox NEO-M8U is both 3.3V and has an integrated IMU. I’m sure that there are more
  2. I’ll check those again
    8.) Oops. Thanks for noticing :slight_smile:

Just my $0.02 :slight_smile:


Oh and you have missed the low pass part between the RF switch and the SMA connector :slight_smile: Are you going to transfer/redesign/tweak the PCB too?

Thanks for noticing :slight_smile:

Yes of course, I’ll do that next!

Wojtek, I think LoRa is locking to a few certain vendors - and a proprietary modulation technology.
In my opinion using LoRa modulation we lose an advantage of having fully Open Source
and vendor agnostic project(LoRa chips are made by a few manufacturers).


Yeah, no place for LoRa in M17 :slight_smile: