iPod Clickwheel Hack

CLICKWHEEL CONNECTOR PINOUT

PIN# *      FUNCTION

1 —– Vbatt (was connedted directly to li-po in ipod; connected to 3V3 supply on board)

2 —– CW_SCL_PIN (clock from clickwheel)

3 —– hw enable? (connected to 3V3)

4—– N/C

5 —– N/C

6 —– CW_SDA_PIN (clickwheel serial data; pulled up with 100K)

7—– hw enable? (connected to 3V3)

8 —– GND

*as indicated on ribbon cable of clickwheel module

*.LOGICSESSION Files Uploaded!

The .logicsession files can be downloaded at the link below. Just remember to change the .jpg extension to .zip. To view the files the logic software can be downloaded for free at www.saleae.com.

https://jasongarr.wordpress.com/wp-content/uploads/2010/01/clickwheel_logicsessionschange-extension-to-zip.jpg

SOURCE CODE!!!

Putting the cart before the horse I have cleaned up my source for this project and turned it in to a driver that can be added easily to any AVR core with little to no modification to the code.  As mentioned in previous posts, details on the reverse engineering process will be added soon.  Untill then feel free to use and modify my code for private non commercial purposes only.

here are the two source files for interfacing the clickwheel. I have added my ‘main.c’ at the bottom as a usage sample.

clickwheel.h

#ifndef CLICKWHEEL_H
#define CLICKWHEEL_H
#endif

//clickwheel data lines
#define DATA_PORT     PORTD
#define DATA_PIN     PIND
#define CW_SDA_PIN    4
#define CW_SCL_PIN    3    //INT1
#define CW_SDA        PIND & (1<<CW_SDA_PIN)
#define CW_SCL        PIND & (1<<CW_SCL_PIN)
//#define CW_SCL_LOW    ((PIND & _BV(7)))
//clickwheel packets
#define CW_CMD_P1        3    //first byte sent in packet
#define CW_BTN_CMD        2    //second byte sent in packet
#define CW_WHEEL_CMD    1    //second byte sent in packet
#define CW_CMD_P4        0    //second byte sent in packet

//clickwheel command ‘cmd’ formatting
#define CW_CMD_CW         0x80    //clockwise scroll event (used for ‘cmd’ stuffing only)
#define CW_CMD_CCW         0x40    //counter-clockwise scroll event (used for ‘cmd’ stuffing only)
#define CW_CMD_FLAG        0x20    //clickwheel new packet arrived flag
#define CW_CMD_PP        0x08    //clickwheel play >>|| pause button pressed
#define CW_CMD_MENU        0x10    //clickwheel menu button pressed
#define CW_CMD_BACK        0x04    //clickwheel back button pressed
#define CW_CMD_FORWARD    0x02    //clickwheel forward button pressed
#define CW_CMD_CBTN        0x01    //clickwheel center button pressed

#define CW_DEADBAND    7    //adjust the sensitivity/speed of the clickwheel. lower=more sensitive

//initialize interrupt and port
extern void uiinit(void);

//function return cmd byte following the clickwheel ‘cmd’ formatting defines
extern unsigned char uiaction(void);

//reset the ui action recieve buffer and cnd flag byte
//this function should be called after responding the the new action
extern void uireset(void);

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clickwheel.c

#include “clickwheel.h”
#include “avr/interrupt.h”

volatile unsigned char cmd;
volatile char posn1, db_compare;
volatile union {
unsigned char byte[4];
unsigned long int word;
} cmd_packet;

ISR(INT1_vect) {
if (CW_SDA) {
cmd_packet.byte[0] |= 0x80;
}

if (((cmd_packet.byte[0] == 128) || (cmd_packet.byte[0] == 192)) && (cmd_packet.byte[3] == 26)) {
cmd = 0x20;
EIMSK &= ~(0x02);
}
else {

cmd_packet.byte[3] = (cmd_packet.byte[3]>>1);
cmd_packet.byte[3] |= (cmd_packet.byte[2]<<7);

cmd_packet.byte[2] = (cmd_packet.byte[2]>>1);
cmd_packet.byte[2] |= (cmd_packet.byte[1]<<7);

cmd_packet.byte[1] = (cmd_packet.byte[1]>>1);
cmd_packet.byte[1] |= (cmd_packet.byte[0]<<7);

cmd_packet.byte[0] = (cmd_packet.byte[0]>>1);
}
}

unsigned char uiaction(void) {
if (cmd == CW_CMD_FLAG ) {

if(cmd_packet.byte[CW_BTN_CMD] != 0){
cmd = cmd_packet.byte[2];
return;
}
else{
if (cmd_packet.byte[CW_WHEEL_CMD] > posn1) {
while (db_compare > CW_DEADBAND) {
cmd = CW_CMD_CW;
db_compare = CW_DEADBAND / 2;
break;
}
db_compare += 1;
}
if (cmd_packet.byte[CW_WHEEL_CMD] < posn1) {
while (db_compare <= 0) {
cmd = CW_CMD_CCW;
db_compare = CW_DEADBAND / 2;
break;
}
db_compare -= 1;
}
posn1 = cmd_packet.byte[CW_WHEEL_CMD];

}
cmd &= ~CW_CMD_FLAG;
cmd_packet.word = 0x00000000;
}
EIMSK |= 0x02;
return cmd;
}

void uiinit() {
//initialize clickwheel port as
DATA_PORT |= (1<<CW_SDA_PIN) | (1<<CW_SCL_PIN);

//configure INT1_vect and pins for sampling clickwheel data transmissions
//on rising edges of the clock
EICRA = 0x0C;    //sets for rising edge interrupt on INT1
EIMSK = 0x02;    //enable interrupts on port INT1
sei();
}

void uireset() {
cmd_packet.word = 0x00000000;
cmd = 0;
}

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main.c

#include “stdlib.h”
#include “avr/io.h”
#include “lcd.h”
#include “clickwheel.h”

#define F_CPU 8000000UL  // 8 MHz

void main(void) {

char buffer[32];
int count;

uiinit();
lcd_init(LCD_DISP_ON);

for(;;) {

//check to see if a new command has been recieved and process command
//and print appropriate button response

switch(uiaction()) {
case CW_CMD_CW:
lcd_gotoxy(0,0);
lcd_puts(“clockwise       “);
count = count + 10;
utoa(count, buffer, 10);
lcd_gotoxy(6,1);
lcd_puts(buffer);
lcd_puts(”     “);
uireset();
break;
case CW_CMD_CCW:
lcd_gotoxy(0,0);
lcd_puts(“counterclockwise”);
count = count – 10;
utoa(count, buffer, 10);
lcd_gotoxy(6,1);
lcd_puts(buffer);
lcd_puts(”     “);
uireset();
break;
case CW_CMD_PP:
lcd_gotoxy(0,0);
lcd_puts(“play/pause      “);

uireset();
break;
case CW_CMD_MENU:
lcd_gotoxy(0,0);
lcd_puts(“menu            “);
uireset();
break;
case CW_CMD_BACK:
lcd_gotoxy(0,0);
lcd_puts(“back            “);
count –;
utoa(count, buffer, 10);
lcd_gotoxy(6,1);
lcd_puts(buffer);
lcd_puts(”     “);
uireset();
break;
case CW_CMD_FORWARD:
lcd_gotoxy(0,0);
lcd_puts(“forward         “);
count ++;
utoa(count, buffer, 10);
lcd_gotoxy(6,1);
lcd_puts(buffer);
lcd_puts(”     “);
uireset();
break;
case CW_CMD_CBTN:
lcd_gotoxy(0,0);
lcd_puts(“center button   “);
uireset();
count = 0;
break;
default:
1;
}

}
}