Computing stuff tied to the physical world

Tinker Pico v1

The Tinker Pico, version 1, is a breakout board to allow simple experimentation with the LPC824 microcontroller series from NXP. The key specifications of this µC are as follows:

  • 32-bit ARM Cortex M0+ (LPC824M201JDH20)
  • 32 KB flash memory and 8 KB RAM
  • clock speed up to 30 MHz (12 MHz on power-up)
  • 16 GPIO pins, of which 5 can be used as 12-bit 1 Msps ADC
  • 2x SPI, 4x I2C, 3x USART, 4x MRTimer, 1x SCTimer/PWM, DMA
  • 20-pin TSSOP package, power supply 1.8 .. 3.6V

An extremely flexible feature of the LPC8xx series µC, is the configurable “switch matrix”. This allows connecting any I/O pin to any digital function (USART, SPI, I2C, PWM, etc).

For ease of use, the Tinker Pico board adds the following properties:

  • 2x 10-pin 0.1″ headers, with the same pinout as the TSSOP chip itself
  • 6-pin FTDI header on the side, supporting uploads, reset, and serial I/O
  • power regulation on-board, which can take up to 5.5V from the FTDI header
  • board size 1.25″ x 0.63″ (31.8 x 16.0 mm), board thickness 1 mm

All components are placed on the bottom, leaving the top free for detailed GPIO pin info:

Tinker pico v1 silkscreen

Note that all these 2x 10 pin assignments are dictated by NXP’s chip layout choices:

  • right next to the pins are the GPIO pin ID’s, as assigned by NXP (0..23, with gaps)
  • A2, A3, A9, A10, and A11 are the analog-capable pins (max 3.3v)
  • C1, C2, C3, and C4 can be used as hardware analog comparators
  • SCL and SDA are open-collector, and support Fast I2C
  • SWD and SWC can be used as hardware-debug pins via SWD/JTAG
  • WU is the wake-up pin to re-activate a fully powered-down µC
  • Xo and Xi can have a crystal or ceramic resonator attached
  • Ci can be used as external clock input for the µC

The PCB itself uses 2 layers of copper (EAGLE files can be found here) – keep in mind again that all the components are mounted on the bottom of this board (shown in blue):

Screen Shot 2015 06 01 at 15 06 59

There is a normally-closed solder jumper near GPIO pin 2, which connects the regulator’s 3.3V output to the µC. This regulator (TPS78233) is an ultra low-power type with only 0.4 µA idle current, which can be disconnected by cutting the jumper trace when powering the board directly from 1.8..3.6V for even lower current consumption.

Speaking of current consumption: the LPC824 can go into different low-power modes, down to 0.2 µA – depending on whether a self-wakeup timer is kept running and whether RAM contents needs to be preserved. Realistically, total board use including the regulator can be kept < 2 µA (with periodic resumes) – that’s over 10 years on a CR2032 coin cell.

Here is the full schematic of the Tinker Pico:

Screen Shot 2015 10 06 at 22 41 51

But hey, any µC is useless until we get some firmware into it, so that’s the next step…

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