write, read and write_then_read

Adafruit_I2CDevice.cpp

@@ -1,6 +1,8 @@
 #include <Adafruit_I2CDevice.h>
 #include <Arduino.h>
 
+//#define DEBUG_SERIAL Serial
+
 Adafruit_I2CDevice::Adafruit_I2CDevice(uint8_t addr, TwoWire *theWire) {
   _addr = addr;
   _wire = theWire;
@@ -28,6 +30,93 @@ bool Adafruit_I2CDevice::detected(void) {
   return false;
 }
 
+bool Adafruit_I2CDevice::write(uint8_t *buffer, size_t len, bool stop) {
+  if (len > 32) {
+    // currently not guaranteed to work if more than 32 bytes!
+    // we will need to find out if some platforms have larger
+    // I2C buffer sizes :/
+#ifdef DEBUG_SERIAL
+    DEBUG_SERIAL.println(F("\tI2CDevice could not write such a large buffer"));
+#endif
+    return false;
+  }
+
+  _wire->beginTransmission(_addr);
+
+  if (_wire->write(buffer, len) != len) {
+#ifdef DEBUG_SERIAL
+    DEBUG_SERIAL.println(F("\tI2CDevice failed to write"));
+#endif
+    return false;
+  }
+
+#ifdef DEBUG_SERIAL
+  DEBUG_SERIAL.print(F("\tI2CDevice Wrote: "));
+  for (int i=0; i<len; i++) {
+    DEBUG_SERIAL.print(F("0x")); 
+    DEBUG_SERIAL.print(buffer[i], HEX); 
+    DEBUG_SERIAL.print(F(", "));
+    if (len % 32 == 31) {
+      DEBUG_SERIAL.println();
+    }
+  }
+  DEBUG_SERIAL.println();
+#endif
+
+
+  return (_wire -> endTransmission(stop) == 0);
+}
+
+bool Adafruit_I2CDevice::read(uint8_t *buffer, size_t len, bool stop) {
+  if (len > 32) {
+    // currently not guaranteed to work if more than 32 bytes!
+    // we will need to find out if some platforms have larger
+    // I2C buffer sizes :/
+#ifdef DEBUG_SERIAL
+    DEBUG_SERIAL.println(F("\tI2CDevice could not read such a large buffer"));
+#endif
+    return false;
+  }
+
+  if (_wire->requestFrom(_addr, (uint8_t)len, stop) != len) {
+    // Not enough data available to fulfill our obligation!
+#ifdef DEBUG_SERIAL
+    DEBUG_SERIAL.println(F("\tI2CDevice did not receive enough data"));
+#endif
+    return false;
+  }
+
+  for (uint16_t i=0; i<len; i++) {
+    buffer[i] = _wire->read();
+  }
+
+#ifdef DEBUG_SERIAL
+  DEBUG_SERIAL.print(F("\tI2CDevice Read: "));
+  for (int i=0; i<len; i++) {
+    DEBUG_SERIAL.print(F("0x")); 
+    DEBUG_SERIAL.print(buffer[i], HEX); 
+    DEBUG_SERIAL.print(F(", "));
+    if (len % 32 == 31) {
+      DEBUG_SERIAL.println();
+    }
+  }
+  DEBUG_SERIAL.println();
+#endif
+
+  return true;
+}
+
+
+bool Adafruit_I2CDevice::write_then_read(uint8_t *write_buffer, size_t write_len, uint8_t *read_buffer, size_t read_len, bool stop) {
+  if (! write(write_buffer, write_len, stop)) {
+    return false;
+  }
+  
+  return read(read_buffer, read_len);
+}
+
+
+
 uint8_t Adafruit_I2CDevice::address(void) {
   return _addr;
 }

Adafruit_I2CDevice.h

@@ -12,4 +12,8 @@ public:
   uint8_t address(void);
   bool begin(void);
   bool detected(void);
+
+  bool read(uint8_t *buffer, size_t len, bool stop=true);
+  bool write(uint8_t *buffer, size_t len, bool stop=true);
+  bool write_then_read(uint8_t *write_buffer, size_t write_len, uint8_t *read_buffer, size_t read_len, bool stop=false);
 };

examples/i2c_readwrite/i2c_readwrite.ino

@@ -0,0 +1,41 @@
+#include <Adafruit_I2CDevice.h>
+
+#define I2C_ADDRESS 0x60
+Adafruit_I2CDevice i2c_dev = Adafruit_I2CDevice(I2C_ADDRESS);
+
+
+void setup() {
+  while (!Serial) { delay(10); }
+  Serial.begin(115200);
+  Serial.println("I2C device read and write test");
+
+  if (!i2c_dev.begin()) {
+    Serial.print("Did not find device at 0x");
+    Serial.println(i2c_dev.address(), HEX);
+    while (1);
+  }
+  Serial.print("Device found on address 0x");
+  Serial.println(i2c_dev.address(), HEX);
+
+  uint8_t buffer[32];
+  // Try to read 32 bytes
+  i2c_dev.read(buffer, 32);
+  Serial.print("Read: ");
+  for (uint8_t i=0; i<32; i++) {
+    Serial.print("0x"); Serial.print(buffer[i], HEX); Serial.print(", ");
+  }
+  Serial.println();
+
+  // read a register by writing first, then reading
+  buffer[0] = 0x0C;  // we'll reuse the same buffer
+  i2c_dev.write_then_read(buffer, 1, buffer, 2, false);
+  Serial.print("Write then Read: ");
+  for (uint8_t i=0; i<2; i++) {
+    Serial.print("0x"); Serial.print(buffer[i], HEX); Serial.print(", ");
+  }
+  Serial.println();
+}
+
+void loop() {
+  
+}