2.4GHz Mouse/Peripherals Expansion Card

I am a firmware developer and electrical engineer currently running a niche PC peripherals company. After seeing the Framework Laptop, I am looking into developing a replacement/alternative to 2.4GHz dongles. I don’t like having a dongle sticking out of a USB A port. USB C dongles stick out even further. Avoiding the dongle by using Bluetooth results in noticeable input latency.

Anyone else here agree?

Unfortunately, a USB port was too thick to contain fully within the Expansion Card, so I checked the spacing for ultra-flat female USB A connectors that insert into a male USB A opening. Still doesn’t fit due to the dongle enclosure being wider than the USB port.

Three options:

  1. Crack open the dongle enclosures and affix the dongle PCB inside the Expansion Card. I’ll use spring contacts on the Expansion Card to connect the dongle’s USB pads and a retaining clip to hold the dongle PCB in place.
  2. License IP from specific peripheral manufacturers so I can develop individual Expansion Cards for each dongle. Essentially I redo layout for an existing dongle and use the official dongle firmware for an Expansion Card version of the dongle.
  3. Don’t license any IP and make a PCB that happens to be compatible with the official firmware of an unnamed manufacturer. I would have my own firmware and peripheral available for sale, but the end user could potentially download and write the relevant official firmware to the Expansion Card on their own if they wanted to use a different device.

#1 has the best compatibility but bad for the end user who has to buy an extra dongle and crack it open.
#2 depends on manufacturers willing to let me work with their IP. Working with me would defray R&D costs for the manufacturer and bring sales of their peripherals from Framework Laptop users. I’ve been trying to contact general counsel for some mice manufacturers, but I likely won’t get any good responses.
#3 gray legal area and I’ll need to discuss with my lawyer first. I would only offer support for my own peripheral in this case. End users wanting to use alternative firmware would need to do the proper research regarding ToS etc. and make their own determinations.

Who here wants a mouse dongle replacement? If so, are you willing to crack open a dongle? What brand mouse or peripheral do you prefer to use?

Have any industry contacts with Logitech, SteelSeries, Corsair, etc.? Please let me know!


Great analysis. I’m not experienced in this field but just wanted to throw my 2c in that a lot of us probably have multiple Logitech Unifying dongles because their mice aren’t known for longevity :wink:

I personally have 2-3 lying around at this moment, so I wouldn’t mind using one as a “donor” for an integrated expansion card solution.

They look to be pretty simple, only issue is if I am able to get that specific set of components may be hard to get firmware. The main chip is the CC2544 data sheet, product information and support | TI.com I have contacted logitech for the schematic as its required by law due to the ftc report https://www.ftc.gov/system/files/documents/reports/nixing-fix-ftc-report-congress-repair-restrictions/nixing_the_fix_report_final_5521_630pm-508_002.pdf

Found a old receiver, not exactly a unifying receiver but uses similar parts just has a firmware lock

may be hard to get firmware

The firmware is easy to get, Logitech has it available for download. The real issue about firmware is the copyright one. You can’t ship it with their firmware installed.

There’s also an older version w/ nRF42 chipset, but the CC2544 chip ends up half the price and has a lot more stock available from chip suppliers. My sources have 250 pcs for the Ti chip and only 19 pcs for the nordic.

Maybe this is a dumb question, but wouldn’t it just be easier to make a regular USB-A adapter that is more inset inside the device, so even if a dongle sticks out it will only stick out a few millimeters and not the full length?


@Theodore_Koniszewski if the port was recessed enough to allow only the thickest part of the dongle to stick out, then you’ll still be saving less than a millimeter compared to a normal USB A port and the dongles that don’t taper in at the USB side would not be recessed at all.


If you want to support Logitech Unifying, it seems like someone already reversed the protocol here https://github.com/RoganDawes/LOGITacker so it should be possible to write a microcontroller firmware that speaks it and shows up as a USB HID device. I don’t know if it would be worth the effort to design a board, write firmware, etc over making a “dongle adapter” but personally I don’t really want to take apart the dongle that came with my mouse.


I ordered some of these converters, I’m really curious to see once my frame.work ships whether I could leave a module out and have a USB-A receiver hiding under the laptop (and eventually try to put a case around it).

Cablecc 5pcs Ultra Mini Type-C USB-C to USB 2.0 OTG Adapter for Cell Phone Tablet & USB Cable & Flash Disk Amazon.com

Logitech has also been shrinking their unifying receivers over time so there may be one slim enough to fit.

Bit too complicated but have exposed power, ground, data + and - with a latching system so you open your receiver dongle with its exposed pads, latch it into the model and off you go. Would have to implement reverse polarity protection.

It’s insane considering it has a chipset and crystal.

I’ve accidentally removed the plastic cap on the end of a unifying receiver, I think it is mostly there to distance the user from the antennas because the actual PCB inside didn’t fill the space entirely.

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For what it’s worth, I would buy one. I like the idea of a recessed USB-A port which would allow the user to just use the mouse/ keyboard/ antenna they already have. This guy on YouTube seems to be doing something similar.