DualCE SPI-GPIO Bridge Technique:

If you’ve ever tried to connect more than one SPI device to your Raspberry Pi, you’ve probably hit a roadblock: the default hardware SPI interface only supports two chip-select (CE) lines.

In this guide, we’ll show you how to connect multiple SPI devices using Python’s spidev library and a clever trick called the DualCE SPI-GPIO Bridge Technique — a method that lets you add unlimited chip select lines without extra hardware.

Why Multiple SPI Devices Can Be a Challenge

SPI is fast and efficient, but:

• Each device needs its own Chip Select (CS) line.
• Raspberry Pi has only CE0 and CE1 by default.
• More than two devices require either extra hardware or manual GPIO control.

The DualCE SPI-GPIO Bridge Technique solves this by combining hardware and software chip select handling.

Hardware Needed

Raspberry Pi with SPI enabled

At least two SPI devices (e.g., MCP3008 ADC, MPU-9250 sensor, flash chips)

Jumper wires

Breadboard

Circuit Wiring

Shared connections:

• MISO → All devices
• MOSI → All devices
• SCLK → All devices

Unique chip select:

• Device 1 → CE0 (GPIO8)
• Device 2 → GPIO17 (manual CS control)
• More devices → Any free GPIO pins for extra CS lines.

Enabling SPI

sudo raspi-config
# Interface Options → SPI → Enable
sudo reboot

Python Code (DualCE SPI-GPIO Bridge Technique)

import spidev
import RPi.GPIO as GPIO
import time

# Setup GPIO for manual CS
GPIO.setmode(GPIO.BCM)
DEVICE2_CS = 17
GPIO.setup(DEVICE2_CS, GPIO.OUT, initial=GPIO.HIGH)

# SPI for CE0
spi0 = spidev.SpiDev()
spi0.open(0, 0)  # Bus 0, CE0
spi0.max_speed_hz = 50000

# SPI for manual CS device (shares same bus)
spi1 = spidev.SpiDev()
spi1.open(0, 0)
spi1.max_speed_hz = 50000

def read_device_0():
    adc = spi0.xfer2([0x01, 0x80, 0x00])
    value = ((adc[1] & 3) << 8) + adc[2]
    return value

def read_device_1():
    GPIO.output(DEVICE2_CS, GPIO.LOW)  # Activate device
    adc = spi1.xfer2([0x01, 0x80, 0x00])
    GPIO.output(DEVICE2_CS, GPIO.HIGH) # Deactivate device
    value = ((adc[1] & 3) << 8) + adc[2]
    return value

try:
    while True:
        val0 = read_device_0()
        val1 = read_device_1()
        print(f"Device 0: {val0}, Device 1: {val1}")
        time.sleep(1)
except KeyboardInterrupt:
    pass
finally:
    spi0.close()
    spi1.close()
    GPIO.cleanup()

Advantages of the DualCE SPI-GPIO Bridge Technique

Works with unlimited SPI devices

No special hardware multiplexer required

Easy to implement in Python

Compatible with any Raspberry Pi model

Conclusion

The DualCE SPI-GPIO Bridge Technique is a simple yet powerful way to expand your Raspberry Pi’s SPI capabilities. By mixing hardware and software chip select handling, you can connect as many devices as you need.