Method transfer

java/libraries/io/src/processing/io/SPI.java:164–188

Transfers data over the SPI bus @param out bytes to send @return bytes read in (array is the same length as out) @webref

(byte[] out)

   *  @webref
   */
  public byte[] transfer(byte[] out) {
    if (NativeInterface.isSimulated()) {
      return new byte[out.length];
    }

    // track the current setting per device across multiple instances
    String curSettings = maxSpeed + "-" + dataOrder + "-" + mode;
    if (!curSettings.equals(settings.get(dev))) {
      int ret = NativeInterface.setSpiSettings(handle, maxSpeed, dataOrder, mode);
      if (ret < 0) {
        System.err.println(NativeInterface.getError(handle));
        throw new RuntimeException("Error updating device configuration");
      }
      settings.put(dev, curSettings);
    }

    byte[] in = new byte[out.length];
    int transferred = NativeInterface.transferSpi(handle, out, in);
    if (transferred < 0) {
      throw new RuntimeException(NativeInterface.getError(transferred));
    } else if (transferred < out.length) {
      throw new RuntimeException("Fewer bytes transferred than requested: " + transferred);
    }
    return in;
  }


  /**