Overview
The spi node enables high-speed serial communication with SPI (Serial Peripheral Interface)
devices. SPI is faster than I2C and ideal for displays, ADCs, DACs, flash memory, and high-bandwidth sensors.
125MHz
Max Speed (Pi 4)
4
Wires (MOSI/MISO/CLK/CS)
2
CE Pins (CS0/CS1)
Full
Duplex
Raspberry Pi SPI Pins
SPI0 (Default)
MOSI (Master Out) GPIO 10 (Pin 19)
MISO (Master In) GPIO 9 (Pin 21)
SCLK (Clock) GPIO 11 (Pin 23)
CE0 (Chip Select 0) GPIO 8 (Pin 24)
CE1 (Chip Select 1) GPIO 7 (Pin 26)
Enable SPI
sudo raspi-config
# Interface Options → SPI → Enable
# Or add to /boot/config.txt:
dtparam=spi=onProperties
| Property | Type | Required | Default | Description |
|---|---|---|---|---|
| device | string | No | "/dev/spidev0.0" | SPI device path |
| speed | number | No | 1000000 | Clock speed in Hz |
| mode | number | No | 0 | SPI mode (0-3) |
| bitsPerWord | number | No | 8 | Bits per word (usually 8) |
| lsbFirst | boolean | No | false | Send LSB first (most devices use MSB) |
SPI Modes
SPI mode defines clock polarity (CPOL) and phase (CPHA). Check your device datasheet.
| Mode | CPOL | CPHA | Description |
|---|---|---|---|
| 0 | 0 | 0 | Clock idle LOW, sample on rising edge (most common) |
| 1 | 0 | 1 | Clock idle LOW, sample on falling edge |
| 2 | 1 | 0 | Clock idle HIGH, sample on falling edge |
| 3 | 1 | 1 | Clock idle HIGH, sample on rising edge |
Inputs
msg.payload
Data to send as array or buffer. Receive buffer of same length.
// Send and receive 3 bytes
msg.payload = [0x01, 0x80, 0x00];
return msg;Outputs
Response
{
"payload": [0x00, 0x07, 0xFF],
"buffer": "<Buffer 00 07 ff>",
"_spi": {
"device": "/dev/spidev0.0",
"speed": 1000000
}
}Common SPI Devices
MCP3008 - ADC
10-bit, 8-channel ADC
Speed: 1MHz max
Mode: 0
MAX7219 - LED Driver
8x8 LED matrix driver
Speed: 10MHz max
Mode: 0
ST7789 - TFT Display
240x240 color LCD
Speed: 62.5MHz max
Mode: 0
W25Q - Flash Memory
NOR flash storage
Speed: 80MHz max
Mode: 0 or 3
Example: Read MCP3008 ADC
Read analog value from channel 0 of MCP3008.
// Function node to read MCP3008 channel 0
var channel = 0;
// Start bit + single-ended + channel
msg.payload = [
0x01, // Start bit
(0x80 | (channel << 4)), // Single-ended, channel select
0x00 // Don't care
];
return msg;// Function node to parse MCP3008 response
var bytes = msg.payload;
// Extract 10-bit value from response
var value = ((bytes[1] & 0x03) << 8) | bytes[2];
// Convert to voltage (assuming 3.3V reference)
msg.payload = {
raw: value,
voltage: (value / 1023) * 3.3
};
return msg;