Some things to try as part of fiddling:

• Using golang as the main language
• Using libmaple instead of the ST libraries

Investigation stages

[[nppilot/boottime]]

Parts

• CPU: Arietta G25
  • 3.3 V only.
  • GPIO pins are 8 mA up to 3.6 V
  • 85 mA @ 5 V
  • On board NCP1529 as 5 V regulator. Specified 2.7 to 5.5 V
  • Watchdog
  • Serial: +3V, 5V, RX, TX, WKP, GND
• GPS: Sparkfun LS20031 (MC-1513)
• IMU: Drotek MPU6050
  • 3.3 V, I2C, drivers/iio/imu/inv_mpu6050
• Receiver: FrSky TFR4
  • 5 V+. PPM output. G25 I/O lines can interrupt on change.
• LCD: MOD-LCD3310
  • 3.3 V, SPI + control, driver
  • pcd8544 based? Or more recent?
• Serial: Sparkfun FTDI
  • GND CTS VCC TXD RXD RTX

Unknown

• Arietta power supply

AT91G25 TC unit

There’s bits of a driver under drivers/misc/atmel_tclib.c and include/linux/atmel_tc.h.

Counter mode has two capture registers that can trigger from a TIOAn line. They are:

• TIOA0: PA21
• TIOA1: PA22
• TIOA2: PA23
• TIOA3: PC2
• TIOA4: PC5
• TIOA5: PC12

Development environment

• GCC 4.8 with gccgo for arm-none-eabi
• OpenOCD works inside VMWare
• OpenOCD plus Signalyzer Lite works

CopterControl basics:

• CopterControl programmer works
• Serial to JSC cable built
• Send and receive serial over the main port

Command:

• Can build and run Mini XPlus kernel

Communications:

• STM32-H103 shows as a USB CDC device
• Measure latency and jitter against x86
• Measure latency and jitter against XPlus

Using golang:

• Build for arm-none-eabi
• Interfacing with C functions
• Interfacing with C types
• When the runtime is needed

Third party components

Qualities for third party components:

• Open license
• Takes patches
• Healthy community?

RTOS:

• NuttX (BSD)
• ChibiOS (GPLv3)
• TNKernel (BSD-like?)

HAL:

• ChibiOS
• libmaple

Drivers and flight:

• CoperControl / OpenPilot
• CrazyFlie
• Ardupilot