Ayke van Laethem

Smartwatch firmware in Go

@ayke@hachyderm.io
@aykevl
@aykevl

PineTime

Hardware

CPU Nordic nRF5832
Cortex-M4 (ARM 32-bit), 64MHz
RAM 64kB
Flash 512kB internal (program)
4MB external (data)
Display 240x240 pixels
12/16 bits/pixel
Features Bluetooth (BLE only)
Heart rate sensor
Accelerometer / step counter

Board package (HAL)

github.com/aykevl/board

  • PineTime
  • GameBoy Advance
  • Gopher Badge
  • Adafruit PyPortal
  • MCH2022 badge
  • Simulator (!)

Simulator

Configuring simulator


if board.Name == "simulator" {
	// Watch dimensions:
	// diagonal: 33mm, side: 23.3mm or 0.91 inch
	board.Simulator.WindowTitle = "GopherWatch"
	board.Simulator.WindowWidth = 240
	board.Simulator.WindowHeight = 240
	board.Simulator.WindowPPI = 261
	board.Simulator.WindowDrawSpeed = time.Second * 12 / 8e6
}

Battery life

  • Serial port
  • DCDC converter
  • Sleep mode: heart rate sensor, flash
  • Accelerometer/step counter
  • External buttons
  • Bluetooth interval

Display hardware

  • 240x240 pixels
  • 16 bits per pixel
  • 8Mbit/s
  • = 8.5fps 😭

Display API

import "tinygo.org/x/drivers/pixel"
						
type Displayer[T pixel.Color] interface {
	Size() (int16, int16)
	DrawBitmap(x, y int16, bitmap pixel.Image[T]) error
	Display() error
	Rotation() drivers.Rotation
}

type ScrollableDisplay[T pixel.Color] interface {
	Displayer[T]
	SetScrollArea(topFixedArea, bottomFixedArea int16)
	SetScroll(line int16)
	StopScroll()
}

TinyGL!

  • Text
  • VBox container
  • List box
  • Scroll container (with hardware scrolling!)
  • Canvas: rectangle, circle, line, text, image
  • Custom widgets
  • ...still missing many things

Future

  • BLE security/privacy
  • translations

Questions?