BLE HID coprocessor for microcontrollers

 

Teensy in green, ESP32-C3 in blue

I have a Teensy 4.1 operating as a Commodore 64 (and Vic-20, and 128, and Apple 1) emulator.  It already supports USB Host (via 5 pin header on top) and web page helper (via USB CDC).

The Teensy doesn't have wireless capability, but I wanted to add BLE keyboard support.  So enter the ESP32-C3 as a coprocessor.  It is running a custom firmware using the NimBLE library to enumerate BLE HID devices in pairing mode, and connects as soon as it finds one. If everything works successfully, it sends HID reports as ASCII over the UART channel (received at Teensy RX pin 0).  

While the Teensy is busy driving the LCD with a bunch of connections, the ESP32-C3 is only wired at 5V input, ground, and a TX pin.  The ESP firmware is built without USB CDC support so that the Serial line defaults to GPIO.  

Shown is a USB only ESP32-C3 board with the advantage of being slightly cheaper.  When I purchased it years ago when ESP32-C3 was relatively new, it was about US$2 on AliExpress.  Looking today, there's even more choices available in all sorts of price ranges and sizes.

So the Teensy is doing what it is good at, and the ESP32-C3 is filling in a wireless connection gap.  The red jumper is provided to be able to pull power.  Though the power connection does have its advantage that the ESP32-C3 has a USB-C port, while the Teensy has a USB-Micro connector.

Look Ma -- no wires!

Mouse, Trackpad, and Gamepad/Joystick are supported as well.  Gamepads and Joysticks will require HID maps which are loaded but not interpreted yet, nor passed on the interface (work to be done).  Joystick support is not implemented yet in my emulators, but stay tuned!

Update (2026-07-03): coprocessor firmware updated to support my custom BLE CBM keyboard sources, and optionally convert standard HID reports to Commodore key scan codes.  By focusing on Commodore scan codes, the integration with the emulators is now simpler, and seamlessly supports more of my keyboards -- while also as being an option, the coprocessor can be used by those that expect standard HID bytes. (Note: no conversion from Commodore to keyboard HID, only the other way around.)

BLE HID Gamepad firmware for M5Stack MiniJoyC

It's not just another pretty face.  Time to get serious about retro gaming.  

Up, Left, Right, Down, Fire (M5) and second button (click joystick).  Not just a d-pad.  Is also mirrored as xpot, ypot, so can do paddle games, or analog joystick games.

Go play some games!

Link: github.com/davervw/m5_minijoystickc_gamepad

Also posted on M5Stack M5Burner

Extremely small emulated C64 and C128

 

This "portable" Commodore 64 and 128 emulator (m5 source code branch) is my work in progress, one in a series of minimalist emulators ported to different hardware targets. Only text (on LCD) with background, foreground, border colors, keyboard entry via USB serial tethered web browser, and general 6502/6510 and C64 memory management emulation is present (no, won't play games, make sound, or do bitmapped graphics) with some D64 emulation [added 7/2/2023].

(Update 7/28/2023) Now with GO 128 command.

GO 128 command

Even my son asked, "Why do you need to do that?"  Well, he has a point.  I wanted a C64 that fit in my pocket or even on my wrist.  And targeting new hardware platforms with my emulator is part of my hobby.

How does it work?  Check out my highly technical drawing.

Now I already here you asking why I didn't connect Bluetooth to the M5Core, because certainly it has Bluetooth as well, and why didn't I use a USB keyboard connected to CoreS3, because it includes USB Host.  But I've had trouble tracking down examples of HID Host examples for M5; client examples are prevalent, but host?

Pictured here is a phone is running Chrome with a custom copy of the html/javascript keyboard adapter including web-serial-polyfill because mobile Chrome doesn't directly include Serial API support.  A Palm Pilot foldable keyboard has a Bluetooth adapter, paired with the phone.   HID keystrokes are captured by the web page, converted to C64 key scan codes, and a list of the active key scan codes (or 64 when keys released) is sent over USB Serial to the M5Core device which is running the C64 ROMs which are tricked into thinking a real keyboard is attached; keystrokes are processed by the C64 KERNAL IRQ as normal.

The M5Core is being powered by the phone.   Why M5Core?  Because it's a polished packaged solution.

Yeah, we could just run a Commodore 64 emulator on the phone, but this way, I could have complete control over the keyboard emulation, what keys are present, how CTRL and Commodore keys work, etc.  And it's just because I can, not because I should.

Why the Palm Keyboard?  Because it folds in my pocket!  And because I had one from back in the day.  Any keyboard you can attach to a phone or computer should work.  And this Bluetooth adapter just makes it so cool, and easier than a tethered keyboard.

The next step is to merge this solution with my Commodore 128 keyboard adapter to completely reject the portability feature.   That would look really cool hooked up to my phone!  Update (7/31/2023): check out YouTube for connection from ItsyBitsy/keyboard to Core Port.A.

C128 Keyboard Adapter Breadboarded Prototype

7/23/2023: PCB prototype keyboard adapter w/ ItsyBitsy

I am excited about my nonsense crazy adventures. Even if only I enjoy them.

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Update (7/2/2023): D64 support is currently working with Core2 only (Basic Core doesn't usually have the additional SPI RAM, but not yet sure why CoreS3 is failing to attach SD).

Update (7/3/2023): Got CoreS3 working with SD switching header to M5Unified.h for that target (was M5Cores3.h) and adding special definition, override logic for SD_CS to use GPIO_NUM_4 instead of default.  See updates to M5Core.h.

Update (7/28/2023): Commodore 128D extended keyboard working with UART connection to Port.A of Core, and Commodore 128 emulation is ported as well.

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