controller/Scan/HP150/scan_loop.c

/* Copyright (C) 2012 by Jacob Alexander
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

// ----- Includes -----

// AVR Includes
#include <avr/interrupt.h>
#include <avr/io.h>
#include <util/delay.h>

// Project Includes
#include <led.h>
#include <print.h>

// Local Includes
#include "scan_loop.h"



// ----- Defines -----

// Pinout Defines
#define DATA_PORT PORTC
#define DATA_DDR   DDRC
#define DATA_PIN      7
#define DATA_OUT   PINC

#define CLOCK_PORT PORTC
#define CLOCK_DDR   DDRC
#define CLOCK_PIN      6

#define RESET_PORT PORTF
#define RESET_DDR   DDRF
#define RESET_PIN      7


// ----- Macros -----

// Make sure we haven't overflowed the buffer
#define bufferAdd(byte) \
		if ( KeyIndex_BufferUsed < KEYBOARD_BUFFER ) \
			KeyIndex_Buffer[KeyIndex_BufferUsed++] = byte



// ----- Variables -----

// Buffer used to inform the macro processing module which keys have been detected as pressed
volatile uint8_t KeyIndex_Buffer[KEYBOARD_BUFFER];
volatile uint8_t KeyIndex_BufferUsed;
volatile uint8_t KeyIndex_Add_InputSignal; // Used to pass the (click/input value) to the keyboard for the clicker

volatile uint8_t currentWaveState = 0;
volatile uint8_t currentWaveDone = 0;
volatile uint8_t positionCounter = 0;


// Buffer Signals
volatile uint8_t BufferReadyToClear;



// ----- Function Declarations -----

void processKeyValue( uint8_t keyValue );
void  removeKeyValue( uint8_t keyValue );



// ----- Interrupt Functions -----

// Generates a constant external clock
ISR( TIMER1_COMPA_vect )
{
	if ( currentWaveState )
	{
		CLOCK_PORT &= ~(1 << CLOCK_PIN);
		currentWaveState--; // Keeps track of the clock value (for direct clock output)
		currentWaveDone--;  // Keeps track of whether the current falling edge has been processed
		positionCounter++;  // Counts the number of falling edges, reset is done by the controlling section (reset, or main scan)
	}
	else
	{
		CLOCK_PORT |=  (1 << CLOCK_PIN);
		currentWaveState++;
	}
}



// ----- Functions -----

// Setup
inline void scan_setup()
{
	// Setup Timer Pulse (16 bit)

	// TODO Clock can be adjusted to whatever (read chip datasheets for limits)
	// This seems like a good scan speed, as there don't seem to be any periodic
	//  de-synchronization events, and is fast enough for scanning keys
	// Anything much more (100k baud), tends to cause a lot of de-synchronization
	// 16 MHz / (2 * Prescaler * (1 + OCR1A)) = 10k baud
	// Prescaler is 1
	cli();
	TCCR1B = 0x09;
	OCR1AH = 0x03;
	OCR1AL = 0x1F;
	TIMSK1 = (1 << OCIE1A);
	CLOCK_DDR = (1 << CLOCK_PIN);
	sei();


	// Initially buffer doesn't need to be cleared (it's empty...)
	BufferReadyToClear = 0;

	// Reset the keyboard before scanning, we might be in a wierd state
	scan_resetKeyboard();
}


// Main Detection Loop
// Since this function is non-interruptable, we can do checks here on what stage of the
//  output clock we are at (0 or 1)
// We are looking for a start of packet
// If detected, all subsequent bits are then logged into a variable
// Once the end of the packet has been detected (always the same length), decode the pressed keys
inline uint8_t scan_loop()
{
	// Read on each falling edge/after the falling edge of the clock
	if ( !currentWaveDone )
	{
		// Sample the current value 50 times
		// If there is a signal for 40/50 of the values, then it is active
		// This works as a very simple debouncing mechanism
		// XXX Could be done more intelligently:
		//  Take into account the frequency of the clock + overhead, and space out the reads
		//  Or do something like "dual edge" statistics, where you query the stats from both rising and falling edges
		//   then make a decision (probably won't do much better against the last source of noise, but would do well for debouncing)
		uint8_t total = 0;
		uint8_t c = 0;
		for ( ; c < 50; c++ )
			if ( DATA_OUT & (1 << DATA_PIN) )
				total++;


		// Only use as a valid signal
		if ( total >= 40 )
		{
			// Reset the scan counter, all the keys have been iterated over
			// Ideally this should reset at 128, however
			//  due to noise in the cabling, this often moves around
			// The minimum this can possibly set to is 124 as there
			//  are keys to service at 123 (0x78)
			// Usually, unless there is lots of interference,
			//  this should limit most of the noise.
			if ( positionCounter >= 124 )
			{
				positionCounter = 0;

				// Clear key buffer
				KeyIndex_BufferUsed = 0;
			}
			// Key Press Detected
			else
			{
				char tmp[15];
				hexToStr( positionCounter, tmp );
				dPrintStrsNL( "Key: ", tmp );

				bufferAdd( positionCounter );
			}
		}

		// Wait until the next falling clock edge for the next DATA scan
		currentWaveDone++;
	}

	// Check if the clock de-synchronized
	// And reset
	if ( positionCounter > 128 )
	{
		char tmp[15];
		hexToStr( positionCounter, tmp );
		erro_dPrint( "De-synchronization detected at: ", tmp );
		errorLED( 1 );

		positionCounter = 0;
		KeyIndex_BufferUsed = 0;

		// A keyboard reset requires interrupts to be enabled
		sei();
		scan_resetKeyboard();
		cli();
	}

	// Regardless of what happens, always return 0
	return 0;
}

// Send data 
uint8_t scan_sendData( uint8_t dataPayload )
{
	return 0;
}

// Signal KeyIndex_Buffer that it has been properly read
void scan_finishedWithBuffer( void )
{
}

// Signal that the keys have been properly sent over USB
void scan_finishedWithUSBBuffer( void )
{
}

// Reset/Hold keyboard
// NOTE: Does nothing with the HP150
void scan_lockKeyboard( void )
{
}

// NOTE: Does nothing with the HP150
void scan_unlockKeyboard( void )
{
}

// Reset Keyboard
void scan_resetKeyboard( void )
{
	info_print("Attempting to synchronize the keyboard, do not press any keys...");
	errorLED( 1 );

	// Do a proper keyboard reset (flushes the ripple counters)
	RESET_PORT |=  (1 << RESET_PIN);
	_delay_us(10);
	RESET_PORT &= ~(1 << RESET_PIN);

	// Delay main keyboard scanning, until the bit counter is synchronized
	uint8_t synchronized = 0;
	while ( !synchronized )
	{
		// Read on each falling edge/after the falling edge of the clock
		if ( !currentWaveDone )
		{
			// Read the current data value
			if ( DATA_OUT & (1 << DATA_PIN) )
			{
				// Check if synchronized
				// There are 128 positions to scan for with the HP150 keyboard protocol
				if ( positionCounter == 128 )
					synchronized = 1;

				positionCounter = 0;
			}

			// Wait until the next falling clock edge for the next DATA scan
			currentWaveDone++;
		}
	}

	info_print("Keyboard Synchronized!");
}