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HDQ routine

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deniska_gus

Joined: 11 Jul 2006
Posts: 42
Location: Minden, Germany

HDQ routine
Posted: Thu Jan 25, 2007 3:59 am

Hi! I'm still searching for this routine for Texas Instruments IC. I don't understand how works this protokol. Maybe you have am example or so. Regards.

Humberto

Joined: 08 Sep 2003
Posts: 1215
Location: Buenos Aires, La Reina del Plata

Posted: Thu Jan 25, 2007 7:51 am

Quote:

I don't understand how works this protokol. Maybe you have am example or so.

You will get a basic explanation of th HDQ single wire protocol in this TI Application Note:
http://focus.ti.com/lit/an/slaa196/slaa196.pdf

Quote:

I'm still searching for this routine for Texas Instruments IC.

Here are the routines, they were built with another compiler for the TI MSP430
processor but it would´nt be so difficult to migrate it to a CCS/PIC:

HDQ.C

Code:

//------------------------------------------------------------------------------
// Library to implement the HDQ single wire interface on MSP430 devices using
// the P1.1 / TA0 pin. Note that an external pull-up resistor is necessary.
//
// A. Dannenberg
// Texas Instruments Inc.
// February 2004
// Built with IAR Embedded Workbench Version: 2.21B
//------------------------------------------------------------------------------
// Include the following line to toggle P1.0 on Timer_A ISR entry/exit
// for use as scope trigger or for measuring ISR execution time.
//#define DEBUG_HDQ
//------------------------------------------------------------------------------
#include "msp430x11x1.h"
#include "HDQ.h"
//------------------------------------------------------------------------------
// Local definitions
enum
{
imWrite,
imWriteE,
imRead,
imReadE,
imDelay
};

// Local variables
static unsigned char ISRMode;
static unsigned char Xfer;
static unsigned char BitCnt;
static unsigned int Ticks;
//------------------------------------------------------------------------------
// void HDQBreak(void)
//
// Local function to send a HDQ break-transmission for providing a safe
// communication start.
//------------------------------------------------------------------------------
static void HDQBreak(void)
{
TACCR0 = TAR + tBreak * 2; // Use double break time
TACCTL0 = OUTMOD_0 + CCIE; // Reset OUT0, enable int
ISRMode = imDelay; // Set ISR mode
LPM0; // Wait for ISR completion
TACCR0 += tBR; // Break recovery time
TACCTL0 = OUTMOD_0 + OUT + CCIE; // Set OUT0, enable int
LPM0; // Wait for ISR completion
}
//------------------------------------------------------------------------------
// void HDQBasicWrite(unsigned char Data)
//
// Local function to output the 8-bit variable 'Data' to the Timer_A.OUT0
// output using the HDQ protocol.
//------------------------------------------------------------------------------
static void HDQBasicWrite(unsigned char Data)
{
Xfer = Data;
TACCTL0 = OUTMOD_0; // Reset OUT0

TACCR0 = TAR;
Ticks = TACCR0; // Bit start time stamp

if (Xfer & 0x01) // LSB == 1?
TACCR0 += tHW1; // Output '1'
else
TACCR0 += tHW0; // Output '0'

TACCTL0 = OUTMOD_4 + CCIE; // Toggle OUT0 on EQU0, en. int
BitCnt = 8; // 8 bits to transfer
ISRMode = imWrite; // Set ISR mode
LPM0; // Wait for ISR completion
}
//------------------------------------------------------------------------------
// void HDQSetup(void)
//
// Exported function to initialize the Timer_A port pin (TA0) that
// is used for HDQ communication
//------------------------------------------------------------------------------
void HDQSetup(void)
{
P1DIR &= ~0x02; // P1.1 as input
P1SEL |= 0x02; // Select TA0 function

#ifdef DEBUG_HDQ
P1OUT &= ~0x01; // P1.0 is scope trigger
P1DIR |= 0x01;
#endif
}
//------------------------------------------------------------------------------
// void HDQWrite(unsigned char Addr, unsigned char Data)
//
// Exported function to write the 8-bit word 'Data' into the 8-bit register
// 'Addr' of the attached HDQ-enabled device.
//------------------------------------------------------------------------------
void HDQWrite(unsigned char Addr, unsigned char Data)
{
TACTL = TASSEL_2 + MC_2; // SMCLK, continuous mode
P1DIR |= 0x02; // P1.1 as in output
HDQBreak(); // Send HDQ break
HDQBasicWrite(Addr | 0x80); // Write to Addr

TACCR0 += tCYCH; // Insert delay
TACCTL0 = OUTMOD_0 + OUT + CCIE; // Set OUT0, enable int
ISRMode = imDelay; // Set ISR mode
LPM0; // Wait for ISR completion

HDQBasicWrite(Data); // Write Data
P1DIR &= ~0x02; // P1.1 as in input
TACTL = 0; // Stop Timer_A
}
//------------------------------------------------------------------------------
// unsigned int HDQRead(unsigned char Addr)
//
// Exported function to read an 8-bit value from the address 'Addr' out of
// the attached HDQ-enabled device. The function will return 0xffff in the
// case of a communication failure (Time-Out).
//------------------------------------------------------------------------------
unsigned int HDQRead(unsigned char Addr)
{
TACTL = TASSEL_2 + MC_2; // SMCLK, continuous mode
P1DIR |= 0x02; // P1.1 as in output
HDQBreak();
HDQBasicWrite(Addr);
P1DIR &= ~0x02; // P1.1 as in input

BitCnt = 8; // 8 bits to transfer
ISRMode = imRead; // Set ISR mode

TACCTL0 = CM_2 + CCIS_0 + SCCI + CAP + CCIE; // Capt. falling edge of P1.1
TACCR1 = TAR + tTO; // Time-Out
TACCTL1 = CCIE; // Enable Time-Out

LPM0; // Wait for ISR completion

TACTL = 0; // Stop Timer_A

if (BitCnt) // All bits received?
return 0xffff; // Error condition (Time-Out)
else
return Xfer; // OK
}
//------------------------------------------------------------------------------
// void Timer_A0_ISR(void)
//
// Timer_A.CCR0 interrupt service function
//------------------------------------------------------------------------------
#pragma vector = TIMERA0_VECTOR
__interrupt void Timer_A0_ISR(void)
{
#ifdef DEBUG_HDQ
P1OUT ^= 0x01; // Toggle scope trigger
#endif

switch (ISRMode)
{
case imWrite :
if (--BitCnt) // Decr and check
{
TACCR0 = Ticks + tCYCH; // Time to cycle completion
ISRMode = imWriteE; // Switch ISR mode
}
else
{
TACCTL0 = OUTMOD_0 + OUT; // Set OUT0, disable int
__bic_SR_register_on_exit(LPM0_bits); // Return active
}
break;
case imWriteE :
Ticks = TACCR0; // Bit start time stamp

if ((Xfer >>= 1) & 0x01) // Process next bit
TACCR0 += tHW1; // Output '1'
else
TACCR0 += tHW0; // Output '0'

ISRMode = imWrite; // Switch ISR mode
break;
case imRead :
TACCTL1 = 0; // Disable Time-Out
TACCR0 += (tDW0 + tDW1) / 2; // Time to middle of bit
TACCTL0 &= ~CAP; // Compare mode
ISRMode = imReadE; // Switch ISR mode
break;
case imReadE :
Xfer >>= 1; // Process next bit
if (TACCTL0 & SCCI) // Check Timer_A latch
Xfer |= 0x80;
if (--BitCnt) // Decr and check
{
TACCTL0 |= CAP; // Capture mode
TACCR1 = TAR + tTO; // Time-Out
TACCTL1 = CCIE; // Enable Time-Out
ISRMode = imRead; // Switch ISR mode
}
else
{
TACCTL0 = OUTMOD_0 + OUT; // Set OUT0, disable int
__bic_SR_register_on_exit(LPM0_bits); // Return active
}
break;
case imDelay :
TACCTL0 &= ~CCIFG; // Disable int
__bic_SR_register_on_exit(LPM0_bits); // Return active
break;
}

#ifdef DEBUG_HDQ
P1OUT ^= 0x01; // Toggle scope trigger
#endif
}
//------------------------------------------------------------------------------
// void Timer_A1_ISR(void)
//
// Timer_A.CCR1-2, TA interrupt service function
//------------------------------------------------------------------------------
#pragma vector = TIMERA1_VECTOR
__interrupt void Timer_A1_ISR(void)
{
if (TAIV == 0x02) // Timer_A.CCR1
{
TACCTL0 = 0; // Disable receiption
TACCTL1 = 0; // Disable Time-Out
__bic_SR_register_on_exit(LPM0_bits); // Return active
}
}

HDQ.H

Code:

#ifndef HDQ_H
#define HDQ_H
//------------------------------------------------------------------------------
// Define the SMCLK frequency
//------------------------------------------------------------------------------
#define ClkFreq 2000000u // Timer clock frequency (Hz)
//------------------------------------------------------------------------------
// Define HDQ Protocol Related Timing Constants
//------------------------------------------------------------------------------
#define tBreak (190 * ClkFreq / 1000000) // HDQ Break Time (190us)
#define tBR (40 * ClkFreq / 1000000) // HDQ Break Recovery Time (40us)
#define tHW1 (40 * ClkFreq / 1000000) // Host sends 1 time (40us)
#define tHW0 (123 * ClkFreq / 1000000) // Host sends 0 time (123us)
#define tCYCH (230 * ClkFreq / 1000000) // Host bit window timing (230us)
#define tDW1 (41 * ClkFreq / 1000000) // Slave sends 1 time (41us)
#define tDW0 (113 * ClkFreq / 1000000) // Slave sends 0 time (113us)
#define tTO (500 * ClkFreq / 1000000) // Time-Out Bit Receiption (500us)
//------------------------------------------------------------------------------
// Exported functions (only for use with C)
//------------------------------------------------------------------------------
#ifdef __STDC__
extern void HDQSetup(void);
extern void HDQWrite(unsigned char Addr, unsigned char Data);
extern unsigned int HDQRead(unsigned char Addr);
#endif
//------------------------------------------------------------------------------
#endif

Humberto

deniska_gus

Joined: 11 Jul 2006
Posts: 42
Location: Minden, Germany


Posted: Fri Jan 26, 2007 2:25 am

Humberto, thank you very much.

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