README: document pin connections

README.md

@@ -30,6 +30,60 @@ Connect the peripherals the following way (STM32F4xx signal; STM32F4xx pin; peri
 
 - *list board to peripheral pin connections*
 
+DRV8825 stepper motor driver (using one timer for PWM output):
+
+- STEP: PA15/TIM2_CH1
+- DIRECTION: PB15
+- nSLEEP: PB14, shorted to nRESET
+- nRESET: PB14, with external 10kOhm pull-down resistor
+- nENABLE: PB13, with external 10kOhm pull-up resistor
+- FAULT: PB12, with external 10kOhm pull-up resistor
+
+reed switch:
+
+- 1: GND
+- 2: PB3
+
+LED driver (using one timer for PWM outputs):
+
+- gate 0: PB6/TIM4_CH1
+- gate 1: PB7/TIM4_CH2
+- gate 2: PB8/TIM4_CH3
+- gate 3: PB9/TIM4_CH4
+
+RGB matrix (using one DMA)
+
+- DR1: PA0
+- DG1: PA1
+- DB1: PA2
+- DR2: PA3
+- DB2: PA4
+- DG2: PA5
+- CLK: PA6
+- LAT: PA7
+- A: PB0
+- B: PB1
+- C: PB2
+- D: PB3
+- OE: PB10
+
+ESP8266 (using one UART):
+
+- RX: PA9/USART1_TX
+- TX: PA10/USART1_RX
+
+free:
+
+- PB4, PB5
+- PA8/TIM1_CH1
+
+used:
+
+- PA12: USB DP
+- PA11: USB DM
+- PC13: LED
+- PC14/PC15: 32kHz XTAL
+
 All pins are configured using `define`s in the corresponding source code.
 
 code