SPI Crystalfontz 632 Problems

Projects Networking, Protocols, and Devices
2

Using SPI_CLOCK_DIV128 results in a SPI clock frequency of 125kHz, which is way above the 18kHz this module maximally supports (see appendix A, min. 55µs clock period). Don't use the SPI hardware interface but use a simple shift out function:

void softSPItransfer(uint8_t data) {
  digitalWrite(SS_PIN, LOW);
  for (uint8_t i = 0; i < 8; i++) {
    if (data & 0x80) {
      digitalWrite(MOSI_PIN, HIGH);
    } else {
      digitalWrite(MOSI_PIN, LOW);
    }
    data <<= 1;
    digitalWrite(SCLK_PIN, LOW);
    delayMicroseconds(27);
    digitalWrite(SCLK_PIN, HIGH);
    delayMicroseconds(27);
  }
  digitalWrite(SS_PIN, HIGH);
}