PS/2 Mouse for any MSP430

rampadc · March 5, 2014

Strangely enough, there aren't a lot of PS/2 mouse codes available for MSP430. The following code allows you to communicate with your PS/2 mouse by remote mode and stream mode (require interrupts). TrackPoint is a mouse module used in ThinkPad keyboards. It uses the PS/2 protocol with some proprietary commands. Keyboards are pretty much the same as mouse, only their reports are simpler.

PS2.h

/*
 * PS2.h
 *
 *  Created on: 14/11/2013
 *      Author: CONG (rampADC)
 */

#ifndef PS2_H_
#define PS2_H_

#include "msp430.h"
#include "stdint.h"

//4MHz XT2
#define delay_us(x) __delay_cycles(x * 4)

#define	CLOCK			0xCC
#define	CLOCK_DIR		P4DIR
#define	CLOCK_OUT		P4OUT
#define CLOCK_IN		P4IN
#define CLOCK_REN		P4REN
#define CLOCK_IFG		0
#define CLOCK_IE		0	
#define CLOCK_IES		0
#define	CLOCK_PIN		BIT7

#define	DATA			0xDA
#define	DATA_DIR		P4DIR
#define	DATA_OUT		P4OUT
#define DATA_IN			P4IN
#define DATA_REN		P4REN
#define DATA_PIN		BIT6

#define	RESET			0xEE
#define	RESET_DIR		P4DIR
#define RESET_OUT		P4OUT
#define RESET_PIN		BIT5

#define	REMOTE_MODE		0xF0
#define	STREAM_MODE		0xEA
#define	RESET_MODE		0xFF

#define	READ_DATA		0xEB
#define	DISABLE_REPORT	0xF5
#define	SET_DEFAULTS	0xF6
#define	ENABLE_REPORT	0xF4
#define	SET_SAMPLE_RATE	0xF3
#define GET_ID			0xF2
#define STATUS_REQUEST	0xE9
#define	SET_RESOLUTION	0xE8
#define	SET_SCALING_2	0xE7
#define SET_SCALING_1	0xE6

#define	TIMING_ERROR	50000

#define	LOW				0
#define	HIGH			1

typedef struct {
	uint8_t state;
	int8_t x;
	int8_t y;
} PS2Data_t;

typedef struct {
	uint8_t state;
	int8_t x;
	int8_t y;
	int8_t z;
} USB_MOUSE_REPORT_t;

void PS2_initialize(void);
void PS2_transmit(uint8_t data);
uint8_t PS2_receive(void);
uint8_t PS2_getBit();
uint8_t PS2_setMode(uint8_t mode);
PS2Data_t PS2_getData(void);

void PS2_setupClockLine(void);
int PS2_dataAvailable(void);
PS2Data_t PS2_streamGetData(void);

USB_MOUSE_REPORT_t PS2_getUSBReport(void);

//trackpoint specific
void Trackpoint_writeToRAM(uint8_t location, uint8_t data);
void Trackpoint_setSensitivity(uint8_t sensitivityFactor);

#endif /* PS2_H_ */

PS2.c

/*
 * PS2.c
 *
 *  Created on: 14/11/2013
 *      Author: CONG (rampADC)
 */

#include "PS2.h"
#include "string.h"
#include "..///printf.h"

void setLine(uint8_t, uint8_t);
uint8_t readLine(uint8_t);

static int dataAvailable = 0;
static int counter = 0;
static PS2Data_t ps2MouseData;
static USB_MOUSE_REPORT_t usbMouseData;

static volatile uint8_t bitcount = 0;
static volatile uint8_t incoming = 0;
static volatile uint8_t incomingParity = 0;
static volatile uint8_t onesCounter = 0;
static volatile uint8_t calculatedParity = 0;
static volatile uint8_t parityOk = 0;
static volatile uint8_t parityChecks[3] = {0,0,0};

uint8_t n, val;

USB_MOUSE_REPORT_t PS2_getUSBReport(void) {
	ps2MouseData = PS2_getData();
	
	usbMouseData.x = ps2MouseData.x;
	usbMouseData.y = -ps2MouseData.y; //by default, ps/2 mouse y-value is opposite to direction moving to
	usbMouseData.state = ps2MouseData.state & 0x07; //only least significant three bits are transferred
	
	//use middle button to scroll
	if(ps2MouseData.state & BIT2) {
		usbMouseData.z = ps2MouseData.y;
	}
	
	return usbMouseData;
}

int Trackpoint_isConnected(void) {
	PS2_transmit(0xE1); //read secondary data
	if(PS2_receive() != 0x01) return 0; //first byte needs to always be 0x01
	uint8_t secondByte = PS2_receive();
	//assuming there will be newer revisions, let's second byte may not be important
	return 1;
}

void Trackpoint_writeToRAM(uint8_t location, uint8_t data) {
	//refer to "Trackpoint System Version 4.0 Engineering Specification" pg. 20
	PS2_transmit(0xE2); 
	PS2_receive(); //ACK
	PS2_transmit(0x81);
	PS2_receive(); //ACK
	PS2_transmit(location);
	PS2_receive(); //ACK
	PS2_transmit(data);
	PS2_receive(); //ACK
}

void Trackpoint_setSensitivity(uint8_t sensitivityFactor) {
	Trackpoint_writeToRAM(0x4A, sensitivityFactor);
}

int PS2_dataAvailable(void) {
	if(dataAvailable) return 1;
	else return 0;
}

PS2Data_t PS2_streamGetData(void) {
	return ps2MouseData;
}

void PS2_initialize(void) {
	//printf("Initializing...\r\n");
	setLine(CLOCK, HIGH);
	setLine(DATA, HIGH);
	//printf("Clock, data idle\r\n");
}

void PS2_transmit(uint8_t data) {
	//printf("Transmitting: %x\r\n",data);
	uint8_t parity = 1;
//	uint8_t data_bak = data;
	uint8_t i;

	setLine(DATA, HIGH);
	setLine(CLOCK, HIGH);
	delay_us(300);
	setLine(CLOCK, LOW);
	delay_us(300);
	setLine(DATA, LOW);
	delay_us(10);
	setLine(CLOCK, HIGH);

	while(readLine(CLOCK) == HIGH);

	for(i = 0; i < 8; i++) {
		if(data & BIT0) {
			setLine(DATA, HIGH);
		} else {
			setLine(DATA, LOW);
		}

		while(readLine(CLOCK) == LOW);
		while(readLine(CLOCK) == HIGH);
		parity ^= (data & BIT0);
		data >>= 1;
	}

	if(parity) {
		setLine(DATA, HIGH);
	} else {
		setLine(DATA, LOW);
	}

	while(readLine(CLOCK) == LOW);
	while(readLine(CLOCK) == HIGH);
	setLine(DATA, HIGH);
	delay_us(50);
	while(readLine(CLOCK) == HIGH);
	while(readLine(CLOCK) == LOW || readLine(DATA) == LOW);

	setLine(CLOCK, LOW);
	//printf("Host: %x\r\n",data_bak);
}

//Get incoming data bit during interrupt caused by CLOCK change
uint8_t PS2_getBit(void) {
	parityOk = 0;
	dataAvailable = 0;

	val = ((DATA_IN & DATA_PIN) ? 1 : 0);
	n = bitcount-1;
	if(n <= 7) {
		incoming |= (val << n);
		if(val) onesCounter++;
	} else if(n == 8) {
		incomingParity = val;
	}
	bitcount++;

	if(bitcount == 11) {
		if(onesCounter % 2) {
			calculatedParity = 0; //not divisible by 2 thus ODD, keep it odd (odd parity)
		} else {
			calculatedParity = 1;
		}

		if(calculatedParity == incomingParity) {
			parityOk = 1;
		}

		switch(counter) {
		case 0:
			parityChecks[0] = parityOk;
			ps2MouseData.state = incoming;
			counter++;
			break;
		case 1: 
			parityChecks[1] = parityOk;
			ps2MouseData.x = incoming;
			counter++;
			break;
		case 2:
			parityChecks[2] = parityOk;
			ps2MouseData.y = -incoming;
			counter = 0;

			if(parityChecks[0] && parityChecks[1] && parityChecks[2]) dataAvailable = 1;
			//reset parities
			memset(&parityChecks, 0, 3);

			break;
		}
		bitcount = 0;
		incoming = 0;
		onesCounter = 0;
		calculatedParity = 0;
		incomingParity = 0;
		parityOk = 0;
	}
	return val;
}

uint8_t PS2_receive(void) {
	//printf("Receiving...\r\n");
	uint8_t data = 0;
	uint8_t i;
	uint8_t bit = 0x01;

	setLine(CLOCK, HIGH);
	setLine(DATA, HIGH);
	delay_us(50);
	while(readLine(CLOCK) == HIGH);

	delay_us(5);
	while(readLine(CLOCK) == LOW);

	for(i = 0; i < 8; i++) {
		while(readLine(CLOCK) == HIGH);
		if(DATA_IN & DATA_PIN) {
			data |= bit;
		}
		while(readLine(CLOCK) == LOW);
		bit <<= 1;
	}

	while(readLine(CLOCK) == HIGH);
	while(readLine(CLOCK) == LOW);
	while(readLine(CLOCK) == HIGH);
	while(readLine(CLOCK) == LOW);

	setLine(CLOCK, LOW);

	//printf("Mouse: %x\r\n",data);
	return data;
}
/*
 * Comment out when clock line does support interrupts
 */

void PS2_setupClockLine(void) {
	//setup interrupts
	CLOCK_DIR &= ~CLOCK_PIN;	//set direction to input
	CLOCK_REN |= CLOCK_PIN;		//enable pull-up
	CLOCK_OUT |= CLOCK_PIN;		//enable pull-up

	CLOCK_IES |= CLOCK_PIN;		//falling
	CLOCK_IFG &= ~CLOCK_PIN;	//interrupt flag cleared
	CLOCK_IE |= CLOCK_PIN;		//interrupt enable for clock
}
 
uint8_t PS2_setMode(uint8_t mode) {
	uint8_t success = 0;

	switch(mode) {
	case REMOTE_MODE:
		PS2_transmit(REMOTE_MODE);
		PS2_receive();				
		break;
	case STREAM_MODE:	
		//setup mouse
		PS2_transmit(STREAM_MODE);
		PS2_receive();
		PS2_transmit(ENABLE_REPORT); 
		PS2_receive();
		break;
	case RESET_MODE:
		//TrackPoint has a reset pin, need to use it.
		RESET_OUT |= RESET_PIN;
		RESET_DIR |= RESET_PIN;
		delay_us(2000000);
		RESET_OUT &= ~RESET_PIN; 
		//For normal PS/2 devices, this should be enough
		PS2_transmit(RESET_MODE);
		PS2_receive();
		PS2_receive();
		PS2_receive();
		break;
	}

	return success;
}

PS2Data_t PS2_getData(void) {
	PS2_transmit(READ_DATA);
	PS2_receive();
	ps2MouseData.state = PS2_receive();
	ps2MouseData.x = PS2_receive();
	ps2MouseData.y = PS2_receive();

	return ps2MouseData;
}

//private functions
uint8_t readLine(uint8_t line) {
	if(line == CLOCK) {
		if(CLOCK_IN & CLOCK_PIN) {
			return 1;
		} else {
			return 0;
		}
	} else {
		if(DATA_IN & DATA_PIN) {
			return 1;
		} else {
			return 0;
		}
	}
}

void setLine(uint8_t line, uint8_t state) {
	if(line == CLOCK) {
		if(state == LOW) {
			CLOCK_DIR |= CLOCK_PIN;		//set direction to output
			CLOCK_OUT &= ~CLOCK_PIN;	//set output to low
		} else {
			CLOCK_DIR &= ~CLOCK_PIN;	//set direction to input
			CLOCK_REN |= CLOCK_PIN;		//enable pull-up
			CLOCK_OUT |= CLOCK_PIN;		//enable pull-up
		}
	} else {
		if(state == LOW) {
			DATA_DIR |= DATA_PIN;		//set direction to output
			DATA_OUT &= ~DATA_PIN;	//set output to low
		} else {
			DATA_DIR &= ~DATA_PIN;	//set direction to input
			DATA_OUT |= DATA_PIN;		//enable pull-up
			DATA_REN |= DATA_PIN;		//enable pull-up 
		}
	}
}

To use this, you need to:

Change CLOCK and DATA ports definitions in PS2.h. I have attempted to use pointers but it was too messy.
Comment PS2_setupClockLine() if your clock line does not support interrupt.
Use an accurate clock. PS/2 timing is strict.
Change the delay multiplier accordingly to your clock frequency. I am still finding a way so the compiler automatically substitute in the correct value.

#define delay_us(x) __delay_cycles(x * 4) //4MHz is used in PS2.h. Find this line, and change it the number '4' if needed.

Test code:

UART Remote mode - works great. Tested with oPossum's tiny printf code. In this example, I am using an external 4MHz crystal. Tested with MSP430F5510

#include <msp430.h> 

#include "PS2.h"

#include "Printf.h"

void initClocksXT2(void);
void initUART(void);

static USB_MOUSE_REPORT_t data;

int main(void) {
	WDTCTL = WDTPW | WDTHOLD;	// Stop watchdog timer

	initClocksXT2();
	initUART();

	PS2_initialize();
	PS2_setMode(RESET_MODE);
	PS2_setMode(REMOTE_MODE);
	
	while(1) {
		data = PS2_getUSBReport();
		printf("x: %i, y: %i, z: %i, LMR: %i%i%i\r\n",data.x,data.y,data.z,data.state & BIT0,data.state & BIT2,data.state & BIT1);
	}
}

void initClocksXT2(void) {
	///XT2 as MCLK and SMCLK  
	P5SEL |= BIT2+BIT3;                       // Port select XT2

	UCSCTL6 &= ~XT2OFF;                       // Enable XT2 
	UCSCTL3 |= SELREF_2;                      // FLLref = REFO
	// Since LFXT1 is not used,
	// sourcing FLL with LFXT1 can cause
	// XT1OFFG flag to set
	UCSCTL4 |= SELA_2;                        // ACLK=REFO,SMCLK=DCO,MCLK=DCO

	// Loop until XT1,XT2 & DCO stabilizes - in this case loop until XT2 settles
	do
	{
		UCSCTL7 &= ~(XT2OFFG + XT1LFOFFG + DCOFFG);
		// Clear XT2,XT1,DCO fault flags
		SFRIFG1 &= ~OFIFG;                      // Clear fault flags
	}while (SFRIFG1&OFIFG);                   // Test oscillator fault flag

	UCSCTL6 &= ~XT2DRIVE0;                    // Decrease XT2 Drive according to
	// expected frequency
	UCSCTL4 |= SELS_5 + SELM_5;               // SMCLK=MCLK=XT2
}

void initUART() {
	//4MHz 9600
	P4SEL = BIT4;
	UCA1CTL1 |= UCSWRST;					 // **Put state machine in reset**
	UCA1CTL1 |= UCSSEL_2;					 // SMCLK
	UCA1BR0 = 0xA0;							 
	UCA1BR1 = 0x01;							 
	UCA1MCTL = UCBRS_5 + UCBRF_0; 
	// over sampling
	UCA1CTL1 &= ~UCSWRST;					 // **Initialize USCI state machine**
}

UART - Stream mode. Tested on the MSP430F5529LP. Using crystal as clock source.

#include <msp430.h> 
#include "Printf.h"
#include "PS2.h"

PS2Data_t mouseData;

uint8_t left = 0;
uint8_t mid = 0;
uint8_t right = 0;
int main(void) {

	WDTCTL = WDTPW | WDTHOLD;	// Stop watchdog timer

	//Testing pins
	P1OUT &= ~BIT0;
	P1DIR |= BIT0;
	P6OUT &= BIT5;
	P6DIR |= BIT5;
	P3OUT &= ~BIT4;
	P3DIR |= BIT4;

	initClocks(); //code stored in another file. just XT2 at 4MHz
	initUART(); //code stored in another file. 4MHz at 9600 baud.

	PS2_initialize();
	PS2_setMode(RESET_MODE);
	PS2_setMode(STREAM_MODE);

	PS2_setupClockLine(); //set up interrupt on clock line

	printf("UART's working fine\r\n");
	while(1) {
		//_BIS_SR(LPM0_bits + GIE);

		if(PS2_dataAvailable()) {
			
			left = PS2_streamGetData().state & BIT0 == BIT0;
			right = PS2_streamGetData().state & BIT1 == BIT1;
			mid = PS2_streamGetData().state & BIT2 == BIT2;
			printf("LEFT: %i, MID: %i, RIGHT: %i ", left, mid, right);
			printf("(%i, %i)\r\n", PS2_streamGetData().x, PS2_streamGetData().y);
		}
	}
}

//CLOCK on P1.4
#pragma vector = PORT1_VECTOR
__interrupt void P1ISR(void) {
	if(CLOCK_IFG & CLOCK_PIN) {
		PS2_getBit(); 
		CLOCK_IFG &= ~CLOCK_PIN;
		//_BIC_SR_IRQ(LPM0_bits);
	}
}

This PS/2 stream code does not work well with USB. Synchronization errors appears. I am still trying to fix this. Use PS2_getUSBReport() to get the report needed for a USB HID mouse.

UPDATE 11/03/2014

To use remote mode with USB, put the mouse reading-report-converting block into a timer interrupt block and set the timer to interrupt I'd say at least 6ms, which is the time it takes for the PS/2 mouse to communicate with my 430 chip. My PS/2 mouse clock operates at 14kHz. Yours may range from 10kHz to 16kHz so increase the time interval if it doesn't work. Better yet, probe it with a logic analyzer to determine the time.

void initTimers() {
	//set TA0CCR0 to time 7ms, assuming 4MHz clock
	TA0CCR0 = 27999;
	//ENABLE CAPTURE/COMPARE INTERRUPT (FOR WHEN TA0CCR0 IS REACHED)
	TA0CCTL0 = CCIE;
	//SMCLK, UP, /1
	TA0CTL = TASSEL_2 + MC_0 + ID_0; //stop it first
}

case ST_ENUM_ACTIVE:
	PS2_setMode(RESET_MODE);
	PS2_setMode(REMOTE_MODE);
	Trackpoint_setSensitivity(0xC0);

	TA0CTL |= MC_1; //start timer
	
	while(1) {
		__bis_SR_register(LPM0_bits + GIE);
	}
	
	break;

#pragma vector = TIMER0_A0_VECTOR
__interrupt void TIMER0_A0_ISR(void) {
	ps2Data = PS2_getData();
	usbData.x = ps2Data.x;
	usbData.y = -ps2Data.y; //by default, ps/2 mouse y-value is opposite to direction moving to
	usbData.state = ps2Data.state & 0x07; //only least significant three bits are transferred

	//use middle button to scroll
	if(ps2Data.state & BIT2) {
		usbData.z = ps2Data.y;
	}

	USBHID_sendReport((void *) &usbData, HID_MOUSE);
}

bluehash · March 7, 2014

@@rampadc Thank you for sharing your code. Very much appreciated!

Just to understand, you are connecting a USB mouse/keyboard to the MSP430?

rampadc · March 8, 2014

Hi bluehash, no, I'm connecting a PS/2 mouse to the MSP430. It's up to the MSP430 to convert those PS/2 reports to USB reports.

Sent from my GT-I9100 using Tapatalk

igor · March 8, 2014

What about voltage? PS/2 uses 5v, but, if memory serves, MSP430 pins are mostly not 5v tolerant.

Are you using converters? Will (some) PS/2 devices work at 3.3 v?

rampadc · March 9, 2014

You can use n-MOSFET as voltage converter like this one: http://www.hobbytronics.co.uk/mosfet-voltage-level-converter. You can also use the 2N7002 if you want SMD, or BSS138 like Sparkfun does.

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PS/2 Mouse for any MSP430

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