IO: Add a byte-variant of I2C.write and SPI.write

gohai · gohai · commit 5a618327547a · 2016-04-03T17:37:46.000+02:00
diff --git a/java/libraries/io/src/processing/io/I2C.java b/java/libraries/io/src/processing/io/I2C.java
@@ -211,18 +211,30 @@ public void write(String out) {
 
   /**
    *  Adds a byte to be written to the attached device
-   *  @param out single byte to be written (0-255)
+   *  @param out single byte to be written, e.g. numeric literal (0 to 255, or -128 to 127)
    *  @see beginTransmission
    *  @see read
    *  @see endTransmission
    */
   public void write(int out) {
-    if (out < 0 || 255 < out) {
-      System.err.println("The write function can only operate on a single byte at a time. Call it with a value from 0 to 255.");
+    if (out < -128 || 255 < out) {
+      System.err.println("The write function can only operate on a single byte at a time. Call it with a value from 0 to 255, or -128 to 127.");
       throw new RuntimeException("Argument does not fit into a single byte");
     }
     byte[] tmp = new byte[1];
     tmp[0] = (byte)out;
     write(tmp);
   }
+
+  /**
+   *  Adds a byte to be written to the attached device
+   *  @param out single byte to be written
+   *  @see beginTransmission
+   *  @see read
+   *  @see endTransmission
+   */
+  public void write(byte out) {
+    // cast to (unsigned) int
+    write(out & 0xff);
+  }
 }
diff --git a/java/libraries/io/src/processing/io/SPI.java b/java/libraries/io/src/processing/io/SPI.java
@@ -182,16 +182,27 @@ public byte[] transfer(String out) {
 
   /**
    *  Transfers data over the SPI bus
-   *  @param out single byte to send
+   *  @param out single byte to send, e.g. numeric literal (0 to 255, or -128 to 127)
    *  @return bytes read in (array is the same length as out)
    */
   public byte[] transfer(int out) {
-    if (out < 0 || 255 < out) {
-      System.err.println("The transfer function can only operate on a single byte at a time. Call it with a value from 0 to 255.");
+    if (out < -128 || 255 < out) {
+      System.err.println("The transfer function can only operate on a single byte at a time. Call it with a value from 0 to 255, or -128 to 127.");
       throw new RuntimeException("Argument does not fit into a single byte");
     }
     byte[] tmp = new byte[1];
     tmp[0] = (byte)out;
     return transfer(tmp);
   }
+
+
+  /**
+   *  Transfers data over the SPI bus
+   *  @param out single byte to send
+   *  @return bytes read in (array is the same length as out)
+   */
+  public byte[] transfer(byte out) {
+    // cast to (unsigned) int
+    return transfer(out & 0xff);
+  }
 }
