This mruby gem provides GPIO, ADC, PWM, I2C and SPI functionality for the Milk-V Duo series of single board computers. It depends on the wiringX C library included in the Milk-V SDK, as well as some Linux /dev
and /sys
access.
The interface and feature set aim to match the lgpio CRuby gem. This gem is primarily meant as a hardware abstraction layer for a future mruby port of denko.
- GPIO Mode/Read/Write
- GPIO Input Alerts
- Alerts are generated by a separate thread, and can be read from a queue in mruby
- Does not use interrupts. Polls pins every ~100 microseconds instead
- Hardware PWM Output
- Hardware I2C
- Hardware SPI
- Only default SPI mode for now (should be SPI mode 0)
- Ultrasonic Read (HC-SR04)
- Pulse Sequence Read (DHT enviro sensors)
- Bit Bang I2C
- Bit Bang SPI
- SPI modes 0 through 3 supported
- Optional LSBFIRST or MSBFIRST transfers
- Bit Bang 1-Wire
- WS2812 addressable LEDs over Hardware SPI
- Only outputs on SPI2 MOSI pin
- SPI clock must be set to 2.4 MHz
- On-off Keying (OOK) Modulated Waves (based on Hardware PWM)
- Carrier generated by hardware PWM. Software modulated with monotonic clock timing.
-
Duo::HardwarePWM
(convenience wrapper for PWM methods) -
Duo::PositionalServo
(based on Hardware PWM) -
Duo::Infrared
(based on OOK waves)- Default frequency: 38 kHz. Default duty cycle: 33.33%
-
Duo::AnalogInput
(based on sysfs SARADC interface)- On GPIO 26 and 27 only
- Always 12-bit resolution (0-4095 range)
- Full scale voltage is only 1.8V, not 3.3V.
- Some features of the Duo are multiplexed onto the same pins.
- Use
duo-pinmux
to set them up BEFORE using them. See official docs for more info. - Run
mruby pinmux_custom.rb
, from the examples folder, to get the pinmux layout used in all examples.
- Download the Linux image for your board, from the official repo.
- Using balenaEtcher or similar, flash the image to a micro SD card.
- Insert the SD card into your Duo and connect it to your computer.
- Download and unzip the mruby binaries for your board, from the releases section of this repo.
- The Milk-V Duo should have created a network interface on your computer, so you can SSH/SCP into it. The default username is
root
and password ismilkv
. - Copy the binaries onto the board:
# Linux scp -O UNZIPPED_BINARY_FOLDER/* root@192.168.42.1:/usr/local/bin
# Mac scp UNZIPPED_BINARY_FOLDER/* root@192.168.42.1:/usr/local/bin
- SSH into the board with
ssh root@192.168.42.1
. - Try the
mirb
shell, or copy over examples from this folder, and try them withmruby FILENAME.rb
. - If you have issues with the examples (specifically PWM), make sure to read the pinmux section above.
- Unless running Ubuntu, set up a virtual machine with Ubuntu 24.04, then install:
sudo apt install wget git make gcc
- Clone mruby and duo-sdk, then enter the mruby directory:
git clone https://github.com/mruby/mruby
git clone https://github.com/milkv-duo/duo-sdk
cd mruby
-
In
mruby/build_config/milkv_duo.rb
:- Set
MILKV_DUO_VARIANT
to the string that matches your board - Uncomment
conf.gem :github => 'denko-rb/mruby-milkv-duo'
(last line), to enable this gem
- Set
-
Cross-compile mruby with:
rake MRUBY_CONFIG=build_config/milkv_duo.rb
. -
The binaries will be in
build/milv_duo/bin/
, relative to themruby
top-level directory. -
Follow the install instructions above to copy them to the board.