HAL eeprom cleanup

Marlin/src/HAL/STM32F1/eeprom_if_iic.cpp

 // Public functions
 // ------------------------
 
-void eeprom_write_byte(uint8_t *pos, unsigned char value) {
+void eeprom_write_byte(uint8_t *pos, uint8_t value) {
   const unsigned eeprom_address = (unsigned)pos;
   return BL24CXX::writeOneByte(eeprom_address, value);
 }

Marlin/src/HAL/shared/eeprom_if.h

 // EEPROM
 //
 void eeprom_init();
-void eeprom_write_byte(uint8_t *pos, unsigned char value);
+void eeprom_write_byte(uint8_t *pos, uint8_t value);
 uint8_t eeprom_read_byte(uint8_t *pos);

Marlin/src/HAL/shared/eeprom_if_i2c.cpp

 // Public functions
 // ------------------------
 
-void eeprom_write_byte(uint8_t *pos, unsigned char value) {
+static void _eeprom_begin(uint8_t * const pos) {
   const unsigned eeprom_address = (unsigned)pos;
-
   Wire.beginTransmission(eeprom_device_address);
-  Wire.write(int(eeprom_address >> 8));   // MSB
-  Wire.write(int(eeprom_address & 0xFF)); // LSB
+  Wire.write(int(eeprom_address >> 8));   // Address High
+  Wire.write(int(eeprom_address & 0xFF)); // Address Low
+}
+
+void eeprom_write_byte(uint8_t *pos, uint8_t value) {
+  _eeprom_begin(pos);
   Wire.write(value);
   Wire.endTransmission();
 
 }
 
 uint8_t eeprom_read_byte(uint8_t *pos) {
-  const unsigned eeprom_address = (unsigned)pos;
-
-  Wire.beginTransmission(eeprom_device_address);
-  Wire.write(int(eeprom_address >> 8));   // MSB
-  Wire.write(int(eeprom_address & 0xFF)); // LSB
+  _eeprom_begin(pos);
   Wire.endTransmission();
   Wire.requestFrom(eeprom_device_address, (byte)1);
   return Wire.available() ? Wire.read() : 0xFF;

Marlin/src/HAL/shared/eeprom_if_spi.cpp

   #define EEPROM_WRITE_DELAY    7
 #endif
 
-uint8_t eeprom_read_byte(uint8_t* pos) {
-  uint8_t v;
-  uint8_t eeprom_temp[3];
-
-  // set read location
-  // begin transmission from device
-  eeprom_temp[0] = CMD_READ;
-  eeprom_temp[1] = ((unsigned)pos>>8) & 0xFF; // addr High
-  eeprom_temp[2] = (unsigned)pos& 0xFF;       // addr Low
-  WRITE(SPI_EEPROM1_CS, HIGH);
-  WRITE(SPI_EEPROM1_CS, LOW);
+static void _eeprom_begin(uint8_t * const pos, const uint8_t cmd) {
+  const uint8_t eeprom_temp[3] = {
+    cmd,
+    (unsigned(pos) >> 8) & 0xFF,  // Address High
+     unsigned(pos)       & 0xFF   // Address Low
+  };
+  WRITE(SPI_EEPROM1_CS, HIGH);    // Usually free already
+  WRITE(SPI_EEPROM1_CS, LOW);     // Activate the Bus
   spiSend(SPI_CHAN_EEPROM1, eeprom_temp, 3);
+                                  // Leave the Bus in-use
+}
+
+uint8_t eeprom_read_byte(uint8_t* pos) {
+  _eeprom_begin(pos, CMD_READ);   // Set read location and begin transmission
+
+  const uint8_t v = spiRec(SPI_CHAN_EEPROM1); // After READ a value sits on the Bus
+
+  WRITE(SPI_EEPROM1_CS, HIGH);    // Done with device
 
-  v = spiRec(SPI_CHAN_EEPROM1);
-  WRITE(SPI_EEPROM1_CS, HIGH);
   return v;
 }
 
-void eeprom_write_byte(uint8_t* pos, uint8_t value) {
-  uint8_t eeprom_temp[3];
-
-  /*write enable*/
-  eeprom_temp[0] = CMD_WREN;
-  WRITE(SPI_EEPROM1_CS, LOW);
-  spiSend(SPI_CHAN_EEPROM1, eeprom_temp, 1);
-  WRITE(SPI_EEPROM1_CS, HIGH);
-  delay(1);
-
-  /*write addr*/
-  eeprom_temp[0] = CMD_WRITE;
-  eeprom_temp[1] = ((unsigned)pos>>8) & 0xFF;  //addr High
-  eeprom_temp[2] = (unsigned)pos & 0xFF;       //addr Low
+void eeprom_write_byte(uint8_t *pos, uint8_t value) {
+  const uint8_t eeprom_temp = CMD_WREN;
   WRITE(SPI_EEPROM1_CS, LOW);
-  spiSend(SPI_CHAN_EEPROM1, eeprom_temp, 3);
+  spiSend(SPI_CHAN_EEPROM1, &eeprom_temp, 1); // Write Enable
+
+  WRITE(SPI_EEPROM1_CS, HIGH);      // Done with the Bus
+  delay(1);                         // For a small amount of time
+
+  _eeprom_begin(pos, CMD_WRITE);    // Set write address and begin transmission
 
-  spiSend(SPI_CHAN_EEPROM1, value);
-  WRITE(SPI_EEPROM1_CS, HIGH);
-  delay(EEPROM_WRITE_DELAY);   // wait for page write to complete
+  spiSend(SPI_CHAN_EEPROM1, value); // Send the value to be written
+  WRITE(SPI_EEPROM1_CS, HIGH);      // Done with the Bus
+  delay(EEPROM_WRITE_DELAY);        // Give page write time to complete
 }
 
 #endif // USE_SHARED_EEPROM