diff --git a/README.md b/README.md
index 55f6fad..e9a5f28 100644
--- a/README.md
+++ b/README.md
@@ -41,6 +41,42 @@ I am wondering whether we can run multiple Dexed instances, in order to recreate
 * Boot
 * Stat playing
 
+
+## Pinout
+
+All devices on Raspberry Pi GPIOs are optional.
+
+__CAUTION:__ All GPIO numbers are [chip numbers](https://pinout.xyz/), not header positions.
+
+|GPIO | Device |  | Function | Direction | Commant|
+|---|---|---|---|---|---|
+|14 | UART |  | TXD |  | OUT |  | serial MIDI|
+|15 | UART |  | RXD |  | IN |  | serial MIDI|
+|18 | DAC |  | CLK |  | OUT|
+|19 | DAC |  | FS |  | OUT|
+|21 | DAC |  | DOUT |  | OUT|
+|02 | I2C |  | SDA |  | IN/OUT |  | used by some DACs|
+|03 | I2C |  | SCL |  | OUT |  | used by some DACs|
+|17 | LCD |  | EN |  | OUT |  | default setting|
+|27 | LCD |  | RS |  | OUT |  | default setting|
+|16 | LCD |  | RW |  | OUT |  | default setting, optional|
+|22 | LCD |  | D4 |  | OUT |  | default setting|
+|23 | LCD |  | D5 |  | OUT |  | default setting|
+|24 | LCD |  | D6 |  | OUT |  | default setting|
+|25 | LCD |  | D7 |  | OUT |  | default setting|
+|05 | ROTARY ENCODER | CLK (ENC A) | IN |  | default setting|
+|06 | ROTARY ENCODER | DT (ENC B) | IN |  | default setting|
+|26 | ROTARY ENCODER | SW |  | IN |  | default setting|
+|12 | PWM AUDIO | PWM0 |  | OUT |  | on Raspberry Pi Zero|
+|13 | PWM AUDIO | PWM1 |  | OUT |  | on Raspberry Pi Zero|
+|07 | SPI |  | /CE1 |  | OUT |  | reserved|
+|08 | SPI |  | /CE0 |  | OUT |  | reserved|
+|09 | SPI |  | MISO |  | IN |  | reserved|
+|10 | SPI |  | MOSI |  | OUT |  | reserved|
+|11 | SPI |  | SCLK |  | OUT |  | reserved|
+|04 | NONE |  |  |  |  |  | can generate clock signal|
+|20 | NONE |  |  |  |  |  | may be used for DAC DIN|
+
 ## Building locally
 
 E.g., to build for Raspberry Pi 4 on a Ubuntu 20.04 build system, you can use the following example. See [`build.yml`](../../tree/main/.github/workflows/build.yml) for complete build steps that create versions for Raspberry Pi 1, 2, 3,and 4 in 32-bit and 64-bit as required.