Bart Massey 2024 Updates by Robert Elia
This tool is designed to find out a decent frame rate and maximum RGB component values to produce a white-looking RGB of reasonable brightness.
See below for UI.
Run with cargo embed --release. You'll need cargo embed, as
cargo run / probe-rs run does not reliably maintain a
connection for printing. See
probe-rs/probe-rs#1235 for the
details.
Additionally, this can also be run without --release to get extra debug information.
Connect the RGB LED to the MB2 as follows:
- Red to P9 (GPIO1)
- Green to P8 (GPIO2)
- Blue to P16 (GPIO3)
- Gnd to Gnd
Connect the potentiometer (knob) to the MB2 as follows:
- Pin 1 to Gnd
- Pin 2 to P2
- Pin 3 to +3.3V
The knob controls the individual settings: frame rate and color levels. Which parameter the knob controls should be determined by which buttons are held.
- No buttons held: Change the frame rate in steps of 10 frames per second from 10..160.
- A button held: Change the blue level from off to on over 16 steps.
- B button held: Change the green level from off to on over 16 steps.
- A+B buttons held: Change the red level from off to on over 16 steps.
The "frame rate" (also known as the "refresh rate") is the time to scan out all three colors. At 30 frames per second, every 1/30th of a second the LED should scan out all three colors. If the frame rate is too low, the LED will appear to "blink". If it is too high, it will eat CPU for no reason.
I think the frame rate is probably set higher than it needs to be right now: it can be tuned lower.
| Parameter | Value |
|---|---|
| Red Level | 15 |
| Green Level | 15 |
| Blue Level | 12 |
| Frame Rate | 50 |
- Commented existing shared code
- Wired up the RGB LED, potentiometer, and buttons to the MB2
- Implemented the UI
- Configured button a for the blue LED (already implemented)
- Configured button b for the green LED
- Configured button a+b for the red LED
- Configured the knob to change the frame rate when no buttons pushed
- Configured the knob to change the LEDs when the corresponding button combo is pushed
- Updated existing code to share the frame rate between RGB and UI structs
Existing code was pretty straightforward to understand and provide the requested
extensions. Since I was experimenting with adding a photoresistor to the MB2, I
ended up having to change how the program is getting the peripherals from the board.
So instead of using the microbit_bsp::Microbit, I needed to directly use embassy_nrf
directly. This was due to not all the analog pins being available in the microbit_bsp.
I have some ongoing experiments with a photoresistor for trying to determine the
brightness of the LEDs. The thinking is if you can determine the brightness of the
LEDs, you can adjust the frame rate and RGB levels to get specific colors based on
RGB values.
- Ongoing experiments with a photoresistor to determine the brightness of the LEDs
- Was not able to get a smooth fps under 50
- Added some macros, they aren't really useful in this case, but I wanted to experiment with them
- Added cargo build and cargo clippy to github actions on push to main