L5 Modem BM818 - Open Firmware


Biktorgj has made a lot of progress on freeing the firmware on the Quectel EG25-G modem used by the PinePhone. He hasn’t touched the proprietary radio firmware, but has managed to replace a lot of the other stuff which is frankly incredible. I didn’t think that it would be possible–I guess that it is one of those issues where nobody has really tried before, so everyone assumed that it would be impossible.

I look forward to seeing what he can do with the BM818 firmware. I wish that I could assist in some way to help him, but this looks like black magic to me.


Reverse engineering is a tedious art. I’ve dabbled in it, but saying I’m an “artist” would be like me bragging to Van Gogh that I know what the difference between red and blue is.

Very cool that he’s giving that modem a shot, I hope progress comes easy.


If Bigtorgj is ever in need of more stuff to do there is also the Simcom SIM7600 to work on…

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Honestly I would like to see some Thales modem for L5. As Thales could manufacture some of their products in Germany or France and give as another choice for a product not made in PRC.
There are Thales modems in the appropriate size for Librem 5.
But anyways. Let us first have BM818 right and then we could think about options.


L5: Broadmobi BM818 Booting…

I couldn't leave all the @Puri_sm #Librem 5 users missing all the fun!
Just getting started, Broadmobi BM818 Booting our custom bootloader and starting (and crashing mid boot) the Linux kernel from the modem distro! pic.twitter.com/wV5rHNgVl9

— Biktor (@biktorgj) July 17, 2022

L5: Modem: Debug UART and EDL access…


Have you bought one and confirmed that it does indeed physically fit inside the Librem 5??

No, but the confidence that it will fit is pretty high, as it is on paper exactly the same as the original L5 Modem (30mm x 42mm x 2.3 mm) and as JR-Fi already successfully fitted a significantly larger modem ( 31.4 x 42 x 3.8) which is proof that there is some tolerance if one is ready to adjust the case.


The Open Modem Firmware for L5 it’s getting closer to it working stage.
Benefits for L5:

  • Power save
  • Temperature save
  • Free as Freedom
  • Security
  • Privacy
  • Hackable
  • Stability

I really wish that we could run and benefit from free modem firmware, but as far as I understand there could be legal issues running unapproved modem firmware. Has anyone something to say about this?


a) It depends on the country.

b) Putting that to one side, the intention mainly relates to control of radio frequency. You will note that the article specifically says that one of the few remaining blackboxes is the firmware component that directly interacts with the RF.

So if you have open firmware that works for the rest of the module, it should be fine to run it.

The risk, as the article says, is that module manufacturers get lazy and lock down the entire module as the easy way of locking down the interaction with the RF.

As far as I am aware noone has the Quectel EG25-G or similar working in the Librem 5 anyway.


@joao.azevedo @Kyle_Rankin can you help to Biktorgj to get BM818 ADSPs or any?


The Biktorgj Open Firmware for Purism GNU Librem 5 it is advancing good so that will available soon i guess. So i pushing this to get done. :joy:
The open firmware is the Achilles Heel to get full success on Librem 5.


Also i will say that the open firmware for Librem 5 will be a lot limited because L5-bm818-modem it has a small Rom so a lot of featues will missing, but crucial features, like powersave,heatsave,bugsave,security,safety,freedom,enablement,reliablement i guess will be.

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What is the size available?

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