RPi Pico... potential new controller?
reddit.com/r/MechanicalKeyboards/comments/l1u...
reddit.comPosted Jan 21, 2021, 9:03 AM UTC
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reddit.comAccording to the Hackaday article, holding the rest button while plugging in mounts as a mass storage device, where you can drag and drop the code onto it.
This should do wonders for adjusting your keymap at the office or getting beginners into tweaking code without the environment setup overhead.
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Yes, this is similar to Adafruit's CircuitPython boards. It's really nice.
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First thing I thought when I saw that was "hmm, that should provide a nice mkb controller..." Then I saw the pro micro and was like "yup... Mkb controller"
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Note that is not 5V-compatible, so it needs external hardware for stuff like ws2812 leds. It's a neat little device, but it doesn't seem to provide a lot of benefits over the STM32 family, besides the price point.
It does have some interesting capabilities, but they don't seem to be too beneficial for most keyboards.
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IIRC, the datasheet for WS2812 requires VSS to be 5V and the DIN to be at least 70% of 5V (3.5). But, there's a picture in this review of which shows an RPi driving a module of WS2812 LEDs:
https://www.tomshardware.com/reviews/raspberry-pi-pico-review
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There is code using its PIO (programmable I/O) to interface WS2812B LEDs, freeing both MCU cores from it.
I think it is more than powerful enough to be able to drive a RGB LED matrix directly from a MCU core otherwise. Using a matrix would enable more LEDs/less power draw than when using WS2812s. Writing the firmware for that would require a skilled programmer, however.
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Level shifting isn't hard. The chip that does it is a dime.
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Are there any available keyboard firmwares yet?
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No, the architecture is basically completely different from current controllers. It'll be a while until someone manages to port a keeb firmware to it.
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It runs micro python which already has support for emulating keyboards (http://docs.micropython.org/en/v1.9.3/pyboard/library/pyb.USB_HID.html), so I don't know about porting a firmware but writing a simple one from scratch should be straight forward.
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I think more suitably: CircuitPython lists it as a supported board, and KMK runs on CircuitPython.
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IIUC, since it uses the Cortex-M0+ processor, the effort required to get keyboard firmware for it would be e.g. adding the HAL definition stuff for ChibiOS to be able to run QMK; or some HAL/PAC for Rust to write firmware for e.g. Keyberon.
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Stupid question but what is the point of using this MCU? You can't run a full linux on it, and a cortex-m0+ is a rather outdated core compared to the other faster arm chips with M4 out there, right? And compared to other MCUs it doesn't have things like analog input.
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https://www.st.com/content/st_com/en/arm-32-bit-microcontrollers/arm-cortex-m0-plus.html
This page claims the Cortex-M0+ is "the most energy efficient Arm processor available for embedded applications with design constraints". I interpret that to mean "it's small and doesn't use a lot of power for what it can do", but I don't know enough about embedded systems to be able to discuss the trade-offs compared to cortex-m4.
"can't run a full linux on it" isn't a disqualifier for designing these embedded systems. These dev boards (RPi Pico, the SparkFun RP2040, etc.) are powerful enough to support running micropython/circuitpython, which is really much more accessible than for prototyping compared to compile/flash loops of C firmware.
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I think it can be a good keyboard controller: low price and usb-C (I hope it has usb-C, right?)
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There's a ProMicro sized version with the same chip available
And it even has usb c!
And it's cheap, too!
Very interested to see where this goes. No 5-pin header for little screens etc sadly but still could be a great option!