An experimental project to customize squawk virtual machine for microcontrollers. Users can write embedded application programs in Java (with CLDC API) that can run on small embedded system without RTOS.

Highlights

• Ported Squawk VM to mbed classic and esp8266
• Implemented aggressive dead code elimination; Static footprint is reduced to less than 128K (including romized classes)
• Optimized interpreter loop
• Provides easy way to add native methods
• Provides API to call HAL layer
• Has been tested on ESP8266, MICROBIT, LPC1768, NUCLEO_L476, and Linux/x86.

Build for mbed

• Install gcc-arm-none-eabi
• Install JDK
• Install mbed cli (tested with 1.7.5)
• git clone https://github.com/tomatsu/squawk
• cd squawk; make
• cd project_gen/targets/mbed; make TARGET=LPC1768 PROJECT=helloworld
• cd /tmp/lpc1768_helloworld; make

Build for ESP8266

• Install toolchain and SDK
• Install JDK
• git clone https://github.com/tomatsu/squawk
• cd squawk; make
• Set environment variable PATH and ESP_SDK For example, export ESP_SDK=$HOME/esp-open-sdk/sdk; export PATH=$HOME/esp-open-sdk/xtensa-lx106-elf/bin:$PATH
• cd project_gen/targets/esp8266; make PROJECT=helloworld
• cd /tmp/esp8266_helloworld; make

Plans

• Documentation
• Test
• CLDC8 support