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SPI Not Working

Espressif ESP32

Severity: Moderate

Source: OnlyErrorCodes.com — Every error code. One place.

ESP32 SPI Not Working — How to Fix It

What Does This Error Mean?

ESP32 SPI not working is almost always caused by incorrect pin assignments, a wrong chip select (CS) pin, or a clock speed that exceeds the device's maximum. Verify MOSI, MISO, SCK, and CS pins in your SPI.begin() call match your physical wiring.

Affected Models

  • ESP32 DevKit
  • ESP32-WROOM-32
  • ESP32-S2
  • ESP32-S3
  • ESP32-C3
  • ESP32 WROVER

Common Causes

  • Wrong GPIO numbers for MOSI, MISO, SCK, or CS in SPI.begin()
  • Chip select (CS) pin not driven LOW before transaction — device not selected
  • SPI clock frequency too high for the connected device
  • 3.3V vs 5V logic mismatch — device expects 5V logic levels
  • SPI mode mismatch — device requires CPOL/CPHA that differs from default Mode 0

How to Fix It

  1. Verify MOSI, MISO, SCK, and CS pin assignments.

    ESP32 default VSPI pins are GPIO 23 (MOSI), 19 (MISO), 18 (SCK), and 5 (CS), but they can be remapped. In your SPI.begin(SCK, MISO, MOSI, CS) call, verify each pin number matches your actual wiring. A single swapped MOSI/MISO will cause no response from the device.

  2. Manually control the CS pin.

    The chip select pin must be driven LOW before starting a transaction and HIGH after it ends. Many libraries expect you to pass the CS pin to the constructor, but if managing manually, call digitalWrite(CS_PIN, LOW) before SPI.transfer() and HIGH after. A CS pin that stays HIGH means the device is never selected.

  3. Reduce the SPI clock frequency.

    Start with SPI.setFrequency(1000000) (1 MHz) regardless of what the device can theoretically support. Once communication works at 1 MHz, gradually increase to the device's maximum rated clock. Long wires and breadboard connections require lower clock speeds.

  4. Check SPI mode (CPOL and CPHA).

    SPI has four modes (0–3) defined by clock polarity and phase. Most common devices use Mode 0 (SPI_MODE0). If your device uses a different mode, specify it: SPI.beginTransaction(SPISettings(1000000, MSBFIRST, SPI_MODE1)). Check the device datasheet for the correct mode.

  5. Check logic voltage compatibility.

    ESP32 GPIO operates at 3.3V. If your SPI device requires 5V logic (older AVR-based modules, some displays), connect a level shifter between the ESP32 and the device. Connecting 5V SPI signals directly to an ESP32 GPIO can damage the chip.

When to Call a Professional

SPI issues are almost always wiring or configuration. Use a logic analyzer or oscilloscope to verify signals if code and wiring appear correct.