Add function to persist register

Author: sebromero

src/I2CDevice.cpp

@@ -8,6 +8,25 @@ I2CDevice::I2CDevice(TwoWire& bus, uint8_t deviceAddress)
 I2CDevice::I2CDevice(uint8_t deviceAddress)
     : bus(Wire), i2cDeviceAddress(deviceAddress) {}
 
+bool I2CDevice::persistRegister(RegisterInfo registerInfo){
+    writeToRegister(DEFAULTS_REGISTER_INFO, registerInfo.address | (1 << 7));
+
+    // Read bit 7 to check if the write is complete. When the write is complete, bit 7 will be 0.
+    // Try 10 times with increasing delay between each try
+    for (int i = 0; i < 10; ++i) {
+        uint8_t defaultsRegisterData = readFromRegister<uint8_t>(DEFAULTS_REGISTER_INFO);
+        if (!(defaultsRegisterData & (1 << 7))) {
+            return true;
+        }
+        // Even a value of 1 us seems to work, but we start with 100 us to be safe.
+        Serial.println("⌛️ Waiting for flash write to complete...");
+        // Exponential sleep duration
+        delayMicroseconds(100 * (2 << i));
+    }
+
+    return false;
+}
+
 bool I2CDevice::connected() {
     bus.beginTransmission(i2cDeviceAddress);
     return bus.endTransmission() == 0;

src/I2CDevice.h

@@ -141,6 +141,12 @@ class I2CDevice {
         return bus.endTransmission() == 0;
     }
 
+    /**
+     * @brief Makes the value of a given register persistent.
+     * @param registerInfo The register to make persistent.
+     */
+    bool persistRegister(RegisterInfo registerInfo);
+
     /**
      * @brief Reference to the I2C bus used by the device.
      */

src/registers.h

@@ -47,5 +47,6 @@ constexpr RegisterInfo ZMOD4410_RHTR_REGISTER_INFO{0xC4, "float", 4};
 constexpr RegisterInfo ZMOD4410_TEMP_REGISTER_INFO{0xC8, "float", 4};
 constexpr RegisterInfo ZMOD4410_INTENSITY_REGISTER_INFO{0xCC, "float", 4};
 constexpr RegisterInfo ZMOD4410_ODOR_CLASS_REGISTER_INFO{0xD0, "uint8", 1};
+constexpr RegisterInfo DEFAULTS_REGISTER_INFO{0xD4, "uint8", 1};
 
 #endif