DonaldBecker
commented
5 years ago In my layout I added a 2x5 pin SMD header that brought out pins that could be mapped.
5V 12V PB8 3.3V PC11 PD0 PA15 PC10 GND PC12
These can be mapped to: Pin Some interesting functions PB8 I2C1_SCL/CAN1_RX PC11 SPI3_MISO / UART4_RX/ USART3_RX PD0 CAN1_RX (Better would be PB9 I2C1_SDA/CAN1_TX) PA15 SPI3_NSS PC10 SPI3_SCK/ UART4_TX/ USART3_TX PC12 SPI3_MOSI/UART5_TX/ USART3_CK
My layout should be considered a proposal rather than a settled design. These are exactly the decisions that end up being "it would have been so much more useful if you made this minor change".
The intent was that this header could be used for a controlling a SPI device, adding serial communication over bluetooth or WiFi, or adding a SPI memory chip. Note that 8 of the pins directly map to a SPI flash pinout.
Obvious drawbacks:
- It almost but not quite supports dual serial ports, a second CAN channel, I2C, etc.
- It almost supports a SD card or SDIO.
- No analog input pins are provided (none are available: 15 of 16 are already used for analog input, 1 for the cam sensor input)
- It could support I2S, but that seems useless here, unless someone uses it as a sound input for knock processing.
The pads are for a 0.1" spaced header, which takes a bunch of room. Unlike the programming header there isn't a specific reason for this. A 0.05" / 1.27mm header would allow more pins or a smaller footprint. The header should be female or shrouded to avoid pins being exposed to accidental contact, especially as 12V is on a vulnerable outside edge.
jharvey
Low-probability scenario: remote tuning via a data modem, data modems probably prefer TTL RS232, can we expose test pads for one of stm32 uart devices?