PineTime

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Specifications

  • BODY:
    • Dimensions: 37.5mm x 40mm x 11mm
    • Weight: 38 grams
    • Build: Zinc Alloy and Plastic
    • IP Rating: IP67 (waterproof to 1 meter)
  • DISPLAY:
    • Type: IPS capacitive touchscreen, RGB 65K colors
    • Size: 1.3 inches
    • Resolution: 240x240 pixels, 1:1 ratio
  • PLATFORM:
    • OS: Various open source RTOS such as Zephyr, FreeRTOS, Mbed, Mynewt, or NuttX. See PineTime RTOS Comparison.
    • SoC: NORDIC Semiconductor nRF52832
    • CPU: 64MHz ARM Cortex-M4F
  • MEMORY:
    • Internal: 512KB Flash, 64KB RAM
    • Additional: SPI NOR 4 MB Flash
  • COMMUNICATION:
    • Bluetooth 5 (including Low Energy)
  • FEATURES:
    • Sensors: Accelerometer, PPG Heart Rate Sensor
    • Actuator: Vibrator
  • BATTERY:
    • Built-in LiPo 170-180mAh battery
    • Charging: Proprietary 2pin 5V 500mA, USB type A plug

SWD Pinout

The devkits have exposed SWD pins for flashing and debugging. The pinout is: PineTime SWD location.jpg

Driving the peripherals

Display

Note: The factory-default software on the PineTime does not auto-detect the display being disconnected when it has already booted. That can cause garbled output, to fix it just restart the PineTime.

The display is driven using the ST7789 display controller. Use the following pins to drive the screen:

PineTime pin ST7789 pin
LCD_SCK (P0.02) SPI clock
LCD_SDI (P0.03) SPI MOSI
LCD_RS (P0.18) Clock/data pin (CD)
LCD_CS (P0.25) Chip select
LCD_RESET (P0.26) Display reset
LCD_BACKLIGHT_{LOW,MID,HIGH} Backlight (active low)

Notes:

  • Chip select must be held low while driving the display. It must be high when using other SPI devices on the same bus (such as external flash storage) so that the display controller won't respond to the wrong commands.
  • SPI must be used in mode 3. Mode 0 (the default) won't work.
  • LCD_DISPLAY_* is used to enable the backlight. Set at least one to low to see anything on the screen.
  • Use SPI at 8MHz (the fastest clock available on the nRF52832) because otherwise refreshing will be super slow.

Battery

Reading whether the PineTime has power attached is easy: simply read the charge indication pin (P0.12). When it is high it is running on battery, when it is low it is charging.

Reading the battery voltage is a bit harder. For that you can use the battery voltage pin on P0.31 (AIN7). The returned value is 12 bits, which means it is 0..4095. You can get the measured voltage with the following formula, assuming a reference voltage of 3.3V (this is configurable in the ADC):

adcVoltage = adcValue / (4095 / 3.3)

The measured voltage is actually half of the actual battery voltage, because the ADC is connected between a voltage divider where both resistors are 1MΩ. This can be corrected by multiplying the value:

batteryVoltage = adcValue * 2 / (4095 / 3.3)

It's often better to avoid floating point values on embedded systems and in this case there is no reason to use float at all, we can just represent the value in millivolts. Therefore the formula can be simplified to:

batteryVoltage = adcValue * 2000 / (4095 / 3.3)
batteryVoltage = adcValue * 2000 / 1241

Converting this voltage to an estimated capacity in percent requires a more complicated algorithm, because Lithium-ion batteries have a non-linear discharge curve.

Datasheets and Schematics

PineTime Schematics

Component Datasheets

Manual / Articles

Development efforts