+++
math = false
highlight = true
tags = []
title = "ST Link v2 clone as a dev board"
summary = "Notes on using an Aluminium case ST Link v2 clone as a development board"
date = 2018-01-01T15:12:38+01:00
draft = false

+++
Notes on using an Aluminium case ST Link v2 clone as a development board.  In summary,
it can:

* Talk to the host over USB
* Blink the built-in LED (!)
* Drive a RGB LED via PWM
* Drive a 40 RGB LED [pHAT](https://shop.pimoroni.com/products/unicorn-phat) over SPI
* Drive a [320x240 LCD](https://www.adafruit.com/product/2478) over fast bitbanged SPI

## Docs

* [Schematic](http://www.avrki.ru/picture/articles/samodelniy_st_link_v2/shemf_st_link_v2.jpg)
* [STM32F103C8 datasheet](http://www.st.com/content/ccc/resource/technical/document/datasheet/33/d4/6f/1d/df/0b/4c/6d/CD00161566.pdf/files/CD00161566.pdf/jcr:content/translations/en.CD00161566.pdf)
* [STM32F103 series reference manual](http://www.st.com/content/ccc/resource/technical/document/reference_manual/59/b9/ba/7f/11/af/43/d5/CD00171190.pdf/files/CD00171190.pdf/jcr:content/translations/en.CD00171190.pdf)

## Programming

I used a Segger J-Link to load the pre-built
[STM32duino bootloader](https://github.com/rogerclarkmelbourne/STM32duino-bootloader).
As the LED is on `PA9`, use the `generic_boot20_pa9.bin` version.

## Pins

Function | Pin | Feedback pin
-------- | --- | ------------
RST | PB6 | PB5
SWDIO | PB14 | PB12
SWCLK | PA5 + PB13 | None
SWIM | PB8 + PB11 | PB7 + PB9 + PB10
LED | PA9 | N/A

The 'feedback' pins have an extra 100 R to 680 R resistor between the
main pin and the feedback pin.  I assume this is used to detect if the
DUT is driving the pin at the same time as the debugger.

## Functions

Port | Default alternate | Remap alternate
---- | ----------------- | ---------------
PA5 | SPI1_SCK, ADC12_IN5 | None
PA9 (LED) | USART1_TX, TIM1_CH2 | None
PB5 | I2C1_SMBAI | TIM3_CH2, SPI1_MOSI
PB6 | I2C1_SCL, TIM4_CH1 | USART1_TX
PB8 | TIM4_CH3 | I2C1_SCL, CANRX
PB7 | I2C1_SDA, TIM4_CH2 | USART1_RX
PB9 | TIM4_CH4 | I2C1_SDA, CANTX
PB10 | I2C2_SCL, USART3_TX | TIM2_CH3
PB11 | I2C2_SDA, USART3_RX | TIM2_CH4
PB12 | SPI2_NSS, I2C2_SMBAI, USART3_CK, TIM1_BKIN | None
PB13 | SPI2_SCK, USART3_CTS, TIM1_CH1N | None
PB14 | SPI2_MISO, USART3_RTS, TIM1_CH2N | None

Or, transposed:

Function | Available features | But...
-------- | ------------------ | ------
I2C1 | SCL, SCL, SDA | SDA is behind a 680R (might be OK)
I2C2 | SDA, SMBAI, SDA | No SCK
SPI1 | SCK, MOSI | MOSI is on a remap, and remap is all or nothing
SPI2 | SCK, MISO, NSS
USART1 | TX, RX | Usable
USART3 | RX, CTS, RTS, CK, TX | TX and RX are on the same pin