From dc6e7c6ea0f6666bb521be66dcb00f1d1200f8c2 Mon Sep 17 00:00:00 2001
From: alanbjohnston <alan.b.johnston@gmail.com>
Date: Sat, 6 Apr 2019 10:22:40 -0400
Subject: [PATCH 1/2] Create i2c_slave_register_read.ino

---
 arduino/i2c_slave_register_read.ino | 61 +++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 arduino/i2c_slave_register_read.ino

diff --git a/arduino/i2c_slave_register_read.ino b/arduino/i2c_slave_register_read.ino
new file mode 100644
index 00000000..a4890778
--- /dev/null
+++ b/arduino/i2c_slave_register_read.ino
@@ -0,0 +1,61 @@
+#include <Wire.h>
+#define I2C_ADDRESS 0x4B
+#define REGISTER_0 0x00
+#define REGISTER_1 0x01
+#define REGISTER_2 0x02
+#define REGISTER_3 0x03
+
+uint8_t reg; // I2C read register
+unsigned int reg_0_value = 41151;  
+unsigned int reg_1_value = 53124;
+unsigned int reg_2_value = 65535;
+unsigned int reg_3_value = 0;
+
+void setup() {
+
+  Wire.begin(I2C_ADDRESS);
+  Wire.onRequest(requestEvent);
+  Wire.onReceive(receiveEvent);
+  pinMode(LED_BUILTIN, OUTPUT);
+  Serial.begin(9600);           // start serial for output
+  Serial.println();
+  Serial.println("Starting");
+}
+
+void loop() {
+  Serial.println("Waiting for register read");
+  delay(5000);
+}
+
+void receiveEvent(int bytes) {
+  // Read the first byte to determine which register is concerned
+  reg = Wire.read();
+    Serial.print("Read register ");
+    Serial.println(reg);
+}
+
+void requestEvent() {
+  // Read from the register variable to know what to send back
+  digitalWrite(LED_BUILTIN, HIGH);
+  if (reg == REGISTER_0) {
+    Wire.write((uint8_t *)&reg_0_value, sizeof(reg_0_value));
+    Serial.print("Writing value ");
+    Serial.println(reg_0_value);
+  } else if (reg == REGISTER_1) {
+    Wire.write((uint8_t *)&reg_1_value, sizeof(reg_1_value));
+    Serial.print("Writing value ");
+    Serial.println(reg_1_value);
+  } else if (reg == REGISTER_2) {
+    Wire.write((uint8_t *)&reg_2_value, sizeof(reg_2_value));
+    Serial.print("Writing value ");
+    Serial.println(reg_2_value);
+  } else if (reg == REGISTER_3) {
+    Wire.write((uint8_t *)&reg_3_value, sizeof(reg_3_value));
+    Serial.print("Writing value ");
+    Serial.println(reg_3_value);
+  } else {
+    Serial.println("Unknown register");
+  }
+  delay(50);
+  digitalWrite(LED_BUILTIN, LOW);
+}

From 4f38f31d6c937c2b59ca4aafd2c47acfbac8528b Mon Sep 17 00:00:00 2001
From: alanbjohnston <alan.b.johnston@gmail.com>
Date: Sat, 6 Apr 2019 10:24:02 -0400
Subject: [PATCH 2/2] Create i2c_master_register_read.ino

---
 arduino/i2c_master_register_read.ino | 53 ++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)
 create mode 100644 arduino/i2c_master_register_read.ino

diff --git a/arduino/i2c_master_register_read.ino b/arduino/i2c_master_register_read.ino
new file mode 100644
index 00000000..e8c7f1a4
--- /dev/null
+++ b/arduino/i2c_master_register_read.ino
@@ -0,0 +1,53 @@
+// Wire Master Reader
+// by Nicholas Zambetti <http://www.zambetti.com>
+
+// Demonstrates use of the Wire library
+// Reads data from an I2C/TWI slave device
+// Refer to the "Wire Slave Sender" example for use with this
+
+// Created 29 March 2006
+
+// This example code is in the public domain.
+
+// modified by Alan Johnston to show reading registers 0 - 3
+// code based on https://forum.arduino.cc/index.php?topic=211587.0
+
+#include <Wire.h>
+#define I2C_ADDRESS 0x4B
+#define REGISTER_0 0x00
+#define REGISTER_1 0x01
+#define REGISTER_2 0x02
+#define REGISTER_3 0x03
+
+uint8_t reg; // I2C read register
+
+void setup() {
+  Wire.begin();        // join i2c bus (address optional for master)
+  Serial.begin(9600);  // start serial for output
+  pinMode(LED_BUILTIN, OUTPUT);
+  Serial.println("Starting");
+}
+
+void loop() {
+  for (reg=0; reg < 4; reg++) {
+    delay(5000);
+    digitalWrite(LED_BUILTIN, HIGH);
+    Wire.beginTransmission(I2C_ADDRESS);
+    Wire.write(reg);
+    Wire.endTransmission();
+    delay(100);
+    digitalWrite(LED_BUILTIN, LOW);
+  
+    
+    Wire.requestFrom(I2C_ADDRESS, 2);    // request 2 bytes from I2C device
+    byte LSB = Wire.read();
+    byte MSB = Wire.read();
+  
+    uint16_t register_value = ((MSB << 8) | LSB);
+    
+    Serial.print("Read ");
+    Serial.print(register_value);
+    Serial.print(" from register ");
+    Serial.println(reg);
+  }
+}