- PC1 - input, range GND to about 3.2V. This pin is not even one of the 5V tolerant ones, so be very careful with your input!
- PA4 - "sine" wave output, about 3.2Vpp
- PA5 - "ramp" (escalator) output, about 3.2Vpp
Note that on the STM32F3 Discovery board, PA5 is connected to the L3GD20 gyroscope. This shouldn't be a problem while the L3GD20 is not being used, but do be careful!
On the STM32F3 Discovery, solder bridge SB10 will connect the STM32F303Bx PB3
pin (SWO output) to the SWO input of the on-board ST-Link programmer. According to the
STM32F3 Discovery User Manual (UM1570, DM00063382), SB10 should come from the
factory soldered, but on my board it is not. In order to use ITM debugging
features (n.b. the Rust cortex-m-rt crate iprintln! macro), I have to
place a jumper from PB3 to CN3 pin 6 (SWO input).
This project uses a custom breakout board to make using the display and pushbuttons easier. This photo of the board details the connections between its header J1, and the ST7735 LCD and pushbuttons. Note that the order of pins on the LCD is reversed from the order of pins on J1: LCD pin 1 is J1 pin 16, while LCD pin 16 is J1 pin 1.
Connections between the breakout board and the STM32F3 Discovery are as follows:
| STM32F3 | ST7735 | Wire[A] | |||
|---|---|---|---|---|---|
| Discovery | J1 | Module | Color | Function | Notes |
| – | 1 | 16 | LED backlight GND | [B] | |
| – | 2 | 15 | orange | LED backlight + | [C] |
| – | 3 | 14 | (SD CS) | ||
| – | 4 | 13 | (SD MOSI) | ||
| – | 5 | 12 | (SD MISO) | ||
| – | 6 | 11 | (SD SCK) | ||
| PB10 | 7 | 10 | (note) | CS | [D] |
| PB13 | 8 | 9 | green | SCK / SCL | |
| PB15 | 9 | 8 | yellow | SDA / MOSI | |
| PB12 | 10 | 7 | blue | A0 / D/C | |
| PB14 | 11 | 6 | brown | RESET | |
| – | 12 | 5 | (no connection) | ||
| – | 13 | 4 | (no connection) | ||
| – | 14 | 3 | (no connection) | ||
| 3V | 15 | 2 | red | VCC | |
| GND | 16 | 1 | black | GND | [B] |
| PD15 | 17 | brown | Button 4 (right) | [E] | |
| PD14 | 18 | white | Button 3 | [E] | |
| PD13 | 19 | grey | Button 2 | [E] | |
| PD12 | 20 | purple | Button 1 (left) | [E] |
Notes:
[A] 'Wire Color' refers to the color of Dupont jumper that I habitually use, and should match the project photos.
[B] The J1-1 LED backlight ground and J1-16 LCD ground are connected by the breakout board.
[C] The breakout board has a 100Ω fixed resistor and 1kΩ variable resistor between J1-2 and the LCD pin 15, for current limiting of the backlight.
[D] The breakout board can connect the LCD CS pin to ground (thereby selecting the LCD controller) by placing a jumper between J2-3 and J2-4. I usually do this instead connecting J1-7 to the microcontroller, unless I'm also using the SD card.
[E] These pins on the breakout board J1 are connected via 220Ω resistors and the normally-open pushbuttons to GND, making them easy to use via a GPIO pin with pull-up.