Hands-free phone system with RN52 Bluetooth module and PIC24FJ64GB002 : Part2

A new board is assembled for this Hands-free phone system, which is equipped with a speaker unit but is not with a microphone unit yet.    On the new board, the PIC microcontroller powers up the RN52 module automatically and controls audio-volume by “-” or “+” key of a keypad.


<< Introduction in Japanese >>

ブルートゥース・ハンズフリー通話の為の PIC24FJ64GB002 マイコン基板を新しく作成した。RN52 と 音声出力アンプはドーター・ボードとして実装し、USB キーパッド、スピーカー、マイクはコネクタにて接続する。新しいシステムでは PIC の初期化に続いて RN52 を自動的に起動する仕様とした。音量はキーパッドのマイナス・キー、プラス・キーで調節する。


Mobile phone  <–  Bluetooth  –>  RN52  <–  UART  –>  PIC24FJ64GB002  <–  USB  –>  Keypad


HF Bluetooth-Part2-1

HF Bluetooth-Part2-2

Inputted numbers are displayed in the first line of the LCD and the current connection status obtained with the Q command is in the second line.


<< PIC microcontroller board >>

New test board remade in March, 2016, is compatible with that in my blog page on Aug. 31, 2014.
( In Japanese : 平成26年8月31日の稿で示したボードを新たに制作 )


Clock and pin connection of the PIC24FJ64GB002 board :

FRC 8 MHz – 96 MHz PLL;
48 MHz for USB Module (96 MHz PLL divide by 2);
32 MHz for System Clock (96 MHz PLL divide by 3);

LED : RB0, RB1;    Switch (pull down) : MCLR, RB2;

LCD (SC1602BBWB-XA-GB-G) : RS – RB7, R/W – GND, E – RB8, Data bus : DB4 – RB9, DB5 – RB13, DB6 – RB14, DB7 – RB15;

RA0 (assigned to U2RX) – RN52 pin 16 TX
RA1 (assigned to U2TX) – RN52 pin 17 RX
RB3 – RN52 pin 21 PWREN (to power up the RN52 module)
RB4 – RN52 pin 3 GIO2
RA4 – RN52 pin 11 GIO9


<< RN52 board >>

pin 3   GIO2 –  PIC pin 12 (RP4/RB4)
pin 11 GIO9 –  PIC pin 11 (RA4)
pin 16 TX     –  PIC pin 2 (RP5/RA0) assigned to U2RX
pin 17 RX     –  PIC pin 3 (RP6/RA1) assigned to U2TX
pin 21 PWREN – switch (pull high) and PIC pin 7 (RB3)
For flow control is not used, RN52 pin 14 RTS is connected with RN52 pin 15 CTS.

Default UART configuration of the RN52 module :
Baud rate : 115,200 Kbps
Bits : 8
Parity : None
Stop bits : 1


<< Amplifier module >>

OEP30W (fully differential, class D, 30W power amplifier board)


<< Microphone circuit >>

Microphone circuit


<< Sample code >>

 (A project of MPLAB X IDE containing HEX.file only)

Based on Microchip Libraries for Applications v2014_07_22


<< Function of this set >>

If you enter a telephone number, RN52 will initiate outgoing call automatically after 3 seconds.

The maximum telephone number is 11 digits.

Enter-key accepts incoming call, initiates outgoing call or terminates call.

Back-space key cancels a last inputted number.

Plus (+) key increases the volume.

Minus (-) key reduces the volume.

PIC-RB2-switch practices a factory reset of RN52.


In Japanese :

<< 操作方法 >>


Enter key:着信応答、強制発信、切断。

Back space:1文字キャンセル。

Plus (+) key : 音量を上げる。

Minus (-)  key : 音量を下げる。

PIC の RB2-switch で RN52 を工場出荷時設定にリセット。