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Neotron-BMC-Pico

Introduction

This firmware is designed to run on an ST Micro STM32F0 (STM32F030K6T6) microcontroller as fitted to the Neotron Pico.

The MCU has:

  • 32-bit Arm Cortex-M0+ Core
  • 3.3V I/O (mostly 5V tolerant)
  • 32 KiB Flash
  • 4 KiB SRAM
  • LQFP-32 package (0.8mm pitch)
Pin Name Signal Function
02 PF0 BUTTON_nPWR Power Button Input (active low)
03 PF1 BUTTON_nRST Reset Button Input (active low)
06 PA0 MON_3V3 3.3V rail monitor Input (1.65V nominal)
07 PA1 MON_5V 5.0V rail monitor Input (1.65V nominal)
08 PA2 nSYS_RESET System Reset Output (active low)
09 PA3 DC_ON PSU Enable Output (active high)
10 PA4 SPI1_nCS SPI Chip Select Input (active low)
11 PA5 SPI1_SCK SPI Clock Input
12 PA6 SPI1_CIPO SPI Data Output
13 PA7 SPI1_COPI SPI Data Input
14 PB0 LED Output for Power LED
15 PB1 SPEAKER PWM Output for Speaker
18 PA8 IRQ_nHOST Interrupt Output to the Host (active low)
19 PA9 USART1_TX UART Transmit Output
20 PA10 USART1_RX UART Receive Input
21 PA11 USART1_CTS UART Clear-to-Send Output
22 PA12 USART1_RTS UART Ready-to-Receive Input
23 PA13 SWDIO SWD Progamming Data Input
24 PA14 SWCLK SWD Programming Clock Input
25 PA15 PS2_CLK0 Keyboard Clock Input
26 PB3 PS2_CLK1 Mouse Clock Input
27 PB4 PS2_DAT0 Keyboard Data Input
28 PB5 PS2_DAT1 Mouse Data Input
29 PB6 I2C1_SCL I²C Clock
30 PB7 I2C1_SDA I²C Data

Note that in the above table, the UART signals are wired as Data Terminal Equipment (DTE) (i.e. like a PC, not like a Modem). Connect the NMBC UART Transmit Output pin to the Input pin of something like an FTDI TTL-232R-3V3 cable.

This design should also be pin-compatible with the following SoCs (although this firmware may need changes):

  • STM32F031K6Tx
  • STM32F042K4Tx
  • STM32F042K6Tx
  • STM32L071KBTx
  • STM32L071KZTx
  • STM32L072KZTx
  • STM32L081KZTx
  • STM32L082KZTx

Note that not all STM32 pins are 5V-tolerant, and the PS/2 protocol is a 5V open-collector system, so ensure that whichever part you pick has 5V-tolerant pins (marked FT or FTt in the datasheet) for the PS/2 signals. All of the parts above should be OK, but they haven't been tested. Let us know if you try one!

SPI Communications Protocol

The SPI interface runs in SPI mode 0 (clock line idles low, data sampled on rising edge) at 1 MHz (higher speeds TBD). It uses frames made up of 8-bit words.

Build Requirements

  1. rustup and Rust
  2. The thumbv6m-none-eabi target
    • run rustup target add thumbv6m-none-eabi
  3. probe-run
    • run cargo install probe-run
  4. flip-link
    • run cargo install flip-link

Then to build and flash for an STM32F031K6T6, connect a probe supported by probe-rs (such as a SEGGER J-Link, or an ST-Link) and run:

DEFMT_LOG=info cargo run --release

You should see logging messages from the board on your terminal. To increase the logging level, try:

Then to build and flash, connect a probe supported by probe-rs (such as a SEGGER J-Link, or an ST-Link) and run:

DEFMT_LOG=debug cargo run --release

Licence

This crate as a whole is licenced under the GNU Public Licence version 3. See:

The top level README file has more information about this choice of license.