Add ability to set I2C baud rate/clock speed

CHANGELOG.md

@@ -11,6 +11,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Ability to invert the display orientation for SSD1306 (new configuration file option).
 - Support for 64 pixel high SSD1306 OLED displays - many thanks to @ctrl_alt_rees for donating a screen!
+- Ability to set I2C clock speed (new configuration file option).
+  * This is useful for allowing larger displays to refresh at a faster speed; see config file for details.
 
 ### Changed
 

include/config.def

@@ -13,6 +13,10 @@
 #define END_SECTION
 #endif
 
+BEGIN_SECTION(system)
+CFG(i2c_baud_rate,			int,						SystemI2CBaudRate,			400000									)
+END_SECTION
+
 BEGIN_SECTION(midi)
 CFG(usb,					bool,						MIDIUSB,					true									)
 CFG(gpio_baud_rate,			int,						MIDIGPIOBaudRate,			31250									)

sdcard/mt32-pi.cfg

@@ -9,6 +9,24 @@
 
 # Default options are marked with an asterisk (*).
 
+# -----------------------------------------------------------------------------
+# System options
+# -----------------------------------------------------------------------------
+[system]
+
+# Set the I2C baud rate/clock speed for all peripherals (Hz).
+#
+# Most peripherals will work fine at the default speed (400KHz "fast mode"),
+# but larger LCD/OLED displays (e.g. 4-line I2C HD44780 and 64 pixel high
+# SSD1306) won't be able to refresh at 60FPS at the default setting.
+#
+# Try increasing this value to 1000000 (1MHz) for a smoother LCD refresh rate.
+# If your display doesn't work, try backing off the speed 100KHz at a time
+# until it does.
+#
+# Values: 100000-1000000 (400000*)
+i2c_baud_rate = 400000
+
 # -----------------------------------------------------------------------------
 # MIDI options
 # -----------------------------------------------------------------------------

src/kernel.cpp

@@ -92,8 +92,8 @@ bool CKernel::Initialize(void)
 	if (bSerialMIDIEnabled && !m_Serial.Initialize(m_Config.MIDIGPIOBaudRate))
 		return false;
 
-	if (!m_I2CMaster.Initialize())
-		return false;
+	// Init I2C; don't bother with Initialize() as it only sets the clock to 100/400KHz
+	m_I2CMaster.SetClock(m_Config.SystemI2CBaudRate);
 
 	if (!m_MT32Pi.Initialize(bSerialMIDIEnabled))
 		return false;