STM32F103CBT6 I/O pin assignments

Capture all the connectivity and I/O pin resource assignment here for the STM32F103CBT6 “Maple Mini” clone board.

Construction will be hand-wired on a small perf board, and a cable will be constructed between the board with the Maple Mini clone and the SPI TFT LCD display mounted on the front of the DMM.

Note that 3 of the status signals that monitor the position of the “function” switches are connected to non-5v tolerant inputs. These signals are pulled low by the switches and seem to rely on the internal pull-ups of the 3870 CPU to pull them high otherwise. Just to be safe, a 22K resistor is connected in series to limit the current.

Maple Mini Pin# Ardunio PinSTM32 Func5v?Signal 3870 Pin
1 Power +5V power into to 3.3V regulator
2 D0 PB11 (SDA2/RX3) Yes fluke st4 11
3 D1 PB10 (SCL2/TX3) Yes fluke func_d 17
4 D2 PB2 (BOOT1) Yes fluke dp 22
5 D3 PB0 LCD D/C
7 D5 PA6 (MISO1) LCD MISO (not presently used; only SPI Master to Slave data sent)
9 D7 PA4 (NSS1) LCD CS
10 D8 PA3 (RX2) (reserved for alternate serial I/O)
11 D9 PA2 (TX2) (reserved for alternate serial I/O)
12 D10 PA1
13 D11 PA0 (reserved SPI CS for 7-segment LED debugging display)
14 Reset
15 D12 PC15 fluke func_c (through 22K resistor) 19
16 D13 PC14 fluke func_b (through 22K resistor) 6
17 D14 PC13 fluke func_a (through 22K resistor) 18
18 VBat
19 AV- / GND
20 AV+ / Vcc
21 Vcc
22 GND
23 D32/Button PB8
24 D15 PB7 (SDA1) Yes fluke w 34
25 D16 PB6 (SCL1) Yes fluke x 35
26 D17 PB5
27 D18 PB4 Yes fluke y 36
28 D19 PB3 Yes fluke z 37
29 D20 PA15 Yes fluke rng_a 3
30 D21 PA14 Yes fluke rng_b 4
31 D22 PA13 Yes fluke rng_c 5
32 D23 PA12 (USB+/RTS1) Yes (unusable)
33 D24 PA11 (USB-/CTS1) Yes (unusable)
34 D25 PA10 (RX1) Yes (console)
35 D26 PA9 (TX1) Yes (console)
36 D27 PA8 (CK1) Yes fluke func_hv 23
37 D28 PB15 (MOSI2) Yes fluke st0 15
38 D29 PB14 (MOSI2) Yes fluke st1 14
39 D30 PB13 (SCK2) Yes fluke st2 13
40 D31 PB12 (NSS2) Yes fluke st3 12
D33 PB1 *(LED)*

Maple Mini Pins