mbed Android Piano

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mbed Android Piano

Page last updated 07 Nov 2016, by Nate Chandler. 0 replies

This project uses the mbed RPC library to interface with a modified Adafruit Blutooth app. The application sends RPC calls to the mbed over the Adafruit Bluefruit LE UART Friend serial connection. The mbed then uses the Class D audio amp and speaker to generate the correct tone.

Hardware Assembly

mbed	Class D Amp	=Speaker	=Bluetooth module
VU	PWR +		Vin
p21	IN+
p27			TXO
p28			RXI
GND	PWR-		GND
GND	IN-		CTS
	OUT+	+
	OUT-	-

Optional potentiometer can placed on VOL pins of Class D amp.

mbed Code

//Code for mbed Android Piano project
//Based on RPC Example code

#include "mbed.h"
#include "mbed_rpc.h"

// Blutooth
Serial pc(p28, p27);

// Define RPC function
void moveTo(Arguments *in, Reply *out);
RPCFunction rpcMove(&moveTo, "moveTo");

// Speaker Control
double pwmVal;
PwmOut PWM(p21);

int main() {
    char buf[256], outbuf[256];
    while(1) {
        //Get Serial Arguments
        pc.gets(buf, 256);
        //Call the static call method on the RPC class
        RPC::call(buf, outbuf);  
    }
}

// Make sure the method takes in Arguments and Reply objects.
void moveTo (Arguments *in, Reply *out){
    pwmVal = in->getArg<float>();
    PWM.period(1.0/(pwmVal));//Set speaker Frequency
    PWM = 0.5;//Set speaker amplitude
}