Merge pull request #50 from adafruit/mcpreg

Add new SPI register type

Adafruit_BusIO_Register.cpp

@@ -101,6 +101,19 @@ bool Adafruit_BusIO_Register::write(uint8_t *buffer, uint8_t len) {
     return _i2cdevice->write(buffer, len, true, addrbuffer, _addrwidth);
   }
   if (_spidevice) {
+    if (_spiregtype == ADDRESSED_OPCODE_BIT0_LOW_TO_WRITE) {
+      // very special case!
+
+      // pass the special opcode address which we set as the high byte of the
+      // regaddr
+      addrbuffer[0] =
+          (uint8_t)(_address >> 8) & ~0x01; // set bottom bit low to write
+      // the 'actual' reg addr is the second byte then
+      addrbuffer[1] = (uint8_t)(_address & 0xFF);
+      // the address appears to be a byte longer
+      return _spidevice->write(buffer, len, addrbuffer, _addrwidth + 1);
+    }
+
     if (_spiregtype == ADDRBIT8_HIGH_TOREAD) {
       addrbuffer[0] &= ~0x80;
     }
@@ -190,6 +203,19 @@ bool Adafruit_BusIO_Register::read(uint8_t *buffer, uint8_t len) {
     return _i2cdevice->write_then_read(addrbuffer, _addrwidth, buffer, len);
   }
   if (_spidevice) {
+    if (_spiregtype == ADDRESSED_OPCODE_BIT0_LOW_TO_WRITE) {
+      // very special case!
+
+      // pass the special opcode address which we set as the high byte of the
+      // regaddr
+      addrbuffer[0] =
+          (uint8_t)(_address >> 8) | 0x01; // set bottom bit high to read
+      // the 'actual' reg addr is the second byte then
+      addrbuffer[1] = (uint8_t)(_address & 0xFF);
+      // the address appears to be a byte longer
+      return _spidevice->write_then_read(addrbuffer, _addrwidth + 1, buffer,
+                                         len);
+    }
     if (_spiregtype == ADDRBIT8_HIGH_TOREAD) {
       addrbuffer[0] |= 0x80;
     }

Adafruit_BusIO_Register.h

@@ -15,13 +15,21 @@ typedef enum _Adafruit_BusIO_SPIRegType {
    */
   AD8_HIGH_TOREAD_AD7_HIGH_TOINC = 1,
 
-  ADDRBIT8_HIGH_TOWRITE = 2,
   /*!<
    * ADDRBIT8_HIGH_TOWRITE
    * When writing to a register you must actually send the value 0x80 +
    * the register address to the device. e.g. To write to the register 0x19 the
    * register value 0x99 is sent and to read 0x19 is sent.
    */
+  ADDRBIT8_HIGH_TOWRITE = 2,
+
+  /*!<
+   * ADDRESSED_OPCODE_LOWBIT_TO_WRITE
+   * Used by the MCP23S series, we send 0x40 |'rd with the opcode
+   * Then set the lowest bit to write
+   */
+  ADDRESSED_OPCODE_BIT0_LOW_TO_WRITE = 3,
+
 } Adafruit_BusIO_SPIRegType;
 
 /*!