Store last command register and avoid resending.

src/modm/driver/gpio/pca9548a_impl.hpp

@@ -29,6 +29,7 @@ modm::Pca9548a<I2cMaster>::setActiveChannel(uint8_t channel)
 	RF_BEGIN();
 
 	if (channel > 7) {
+		RF_RETURN(false);
 		channel = 0;
 	}
 
@@ -46,6 +47,7 @@ modm::Pca9548a<I2cMaster>::readCommandRegister(uint8_t &command_register)
 
 	this->transaction.configureRead(buffer, 1);
 	command_register = buffer[0];
+	current_command_register = command_register;
 
 	RF_END_RETURN_CALL( this->runTransaction() );
 }
@@ -56,6 +58,12 @@ modm::Pca9548a<I2cMaster>::writeCommandRegister(uint8_t command_register)
 {
 	RF_BEGIN();
 
+	if (current_command_register == command_register) {
+		// No change, return without bus operation
+		RF_RETURN(true);
+	}
+	current_command_register = command_register;
+
 	buffer[0] = command_register;
 	this->transaction.configureWrite(buffer, 1);