Deciphering GON Nerdy v2 PCB Bluetooth

[BenlewisMAV]

Hey all

Long time lurker here, just wondering if anyone can help try and Bluetooth-ify my GON nerdy v2 PCB!
I bought it years ago and finally got around to finishing it off and using it in anger when the pandemic hit. I designed and machined an aluminium and acrylic case for it but it’s super heavy (photos to come) so I’ve stuck it in a clear plastic case for now. The lighting effect looks great and the lighter weight isn’t a bad thing.

Anyway I’ve got quite a bit of info from GON keyboard works website about the Bluetooth parts, including the Bluetooth module name (FB155BC_S) - but it’s basically impossible to buy from anywhere with any kind of confidence!
So my first question is, is there an alternative that would be compatible? Bluetooth 4/5 would be nice 😁 Physical packaging isn’t a concern (happy to solder wires if needs be), but just in terms of communication  protocol, pinouts, etc?
And the second is - what are the x2 ‘PWIC’s he lists in the kit? (3 leg and 5 leg)
I’m guessing 1 of them is a voltage regulator (maybe the 3 pin?) perhaps to provide the Bluetooth module with 3.3v?..

Any help on this would be much appreciated  I’d rather not go the route of adding extra external Bluetooth transmitters (e.g. usb host shield > micro arduino > Adafruit bluefruit / handheld scientific Bluetooth adapter or whatever), it would be neat to retain the GON nerdy Bluetooth keyboard shortcuts and battery indication.

Thanks in advance, Ben

[BenlewisMAV]

Also for reference here’s some close up images of the components in question. The resistors and capacitors I think I’m good with finding, it’s just the ‘PWIC’ as GON called them. And tracking down the Bluetooth module! (Or ideally a more modern compatible equivalent)

[BenlewisMAV]

Here is the spec sheet for the tricky-to-find Bluetooth module
https://fccid.io/U8D-FB155BC/User-Manual/User-Manual-2680545.pdf

And the key bits (pinout images below)

I’m wondering if I can just use most generic Bluetooth modules.. (like an RN42)

So I think I’ve identified the markings on the AVX Tantalum Capacitors. The markings look like ‘106 C’ which makes them 10uF and 16v. I think they are case size C. The rest of the code looks like ‘06L82’, which apparently is an ID code, not sure of the relevance.
The 3 leg PWIC is likely a 3.3v (as most Bluetooth modules seem to be 3.3v) voltage regulator in an SOT 23 package. After a bit more digging I’m beginning to think the 5 leg PWIC as actually a very compact battery charging/management chip for the lithium polymer cell - something like this https://uk.rs-online.com/web/p/battery-management/7386360/
Although that might not be exactly suitable for this cell.

[BenlewisMAV]

So after a little more digging, it is indeed the Microchip MCP73831T-2ACI/OT, Battery Charge Controller IC, 3.75 to 6 V 5-Pin, SOT-23 for the 5 leg ‘PWIC’
- the markings starting with ‘KD’ in the spec. sheet gave it away!

The rest of the order looks like this;
- 2x AVX 10μF Polymer Tantalum Capacitor 16V dc, T## Series
- 1x Microchip MCP73831T-2ACI/OT (Battery charge controller)
- 1x Microchip MCP1700T-3302E/TT (3.3v linear regulator)
- Any 2kOhm - 0805 (2012M) Package Resistor
- Any 330Ohm - 0805 (2012M) Package Resistor
- Any 820Ohm - 0805 (2012M) Package Resistor
I’ll try them out and confirm they are the correct parts but I’m pretty confident after seeing the markings match up from GON’s page to the component Datasheets.

Just need to do a bit of digging into the Bluetooth module now. I’ve got some fairly common/cheap HC-05 modules that I’m looking to reprogram to RN-42 HID Bluetooth modules. The RN-42 uses UART communication and Support Bluetooth 2.1 like the GON Module so fingers crossed with a couple of software tweak (likes the communication Baud rate) will hook right up.

[BenlewisMAV]

So the parts from RS components arrived, and are all soldered on. I didn’t need the resistors as the board already had them fitted (I didn’t bother to check as I’ll use them on other projects anyway). Interestingly the 820ohm resistor shown in on the GON website was fitted with a 330ohm resistor on the PCB. The PCB also has ‘330ohm’ printed on it, so it wasn’t just a mistake, perhaps just a revision change..

I also converted the HC-05 Bluetooth module I had to the RN42 firmware. Sadly the 2 HC05’s I bought recently seem to be the ‘fake’ versions that have made ripples in Arduino circles. The technically aren’t fakes, they still function as HC-05s, but use a lesser hardware chip that can’t be reflashed to RN42 HID firmware.

The plan was to take the HID/serial data that was being sent out of the GON keyboard microcontroller
(on TX/transmit and RX/receive pins 20 and 21
https://www.arduino.cc/en/uploads/Hacking/32U4PinMapping.png)
and send it to the RN42-converted HC-05. Both the RN42 and the original FB155BC Bluetooth module it is replacing use AT commands and Bluetooth 2.1 so I thought they would be mostly compatible. I tested the RN42 by itself and everything seems great, it is recognised by my phone as a Bluetooth HID keyboard/mouse combo and I can send inputs to control the phone over serial (Ardiuno serial monitor or PuTTY).

After trying to hook up the RN42 Bluetooth module to pins 20/21 on the keyboard things weren’t so great..