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controller/Scan/UnivacF3W9/scan_loop.c

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/* 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 REQUEST_PORT PORTD
#define REQUEST_DDR DDRD
#define REQUEST_PIN 3
#define DATA_READ PIND
#define DATA_PORT PORTD
#define DATA_DDR DDRD
#define DATA_PIN 2
#define MAX_SAMPLES 10
#define MAX_FAILURES 3731
#define PACKET_STORAGE 24 // At worst only 8 packets, but with you keypresses you can get more
// ----- Macros -----
#define READ_DATA DATA_READ & (1 << DATA_PIN) ? 0 : 1
#define REQUEST_DATA() REQUEST_DDR &= ~(1 << REQUEST_PIN) // Start incoming keyboard transfer
#define STOP_DATA() REQUEST_DDR |= (1 << REQUEST_PIN) // Stop incoming keyboard data
// 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;
// ----- Function Declarations -----
void processPacketValue( uint16_t packetValue );
// ----- Interrupt Functions -----
// XXX - None Required
// ----- Functions -----
// Setup
// This setup is very simple, as there is no extra hardware used in this scan module, other than GPIOs.
// To be nice, we wait a little bit after powering on, and dump any of the pending keyboard data.
// Afterwards (as long as no keys were being held), the keyboard should have a clean buffer, and be ready to go.
// (Even if keys were held down, everything should probably still work...)
inline void scan_setup()
{
// Setup the DATA pin
DATA_DDR &= ~(1 << DATA_PIN); // Set to input
DATA_PORT |= (1 << DATA_PIN); // Set to pull-up resistor
// Setup the REQUEST pin
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REQUEST_PORT |= (1 << REQUEST_PIN); // Set to output
STOP_DATA(); // Set the line high to stop incoming data
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REQUEST_DATA();
DDRD |= (1 << 4);
PORTD &= ~(1 << 4);
// Message
info_print("Pins Setup");
// Reset the keyboard before scanning, we might be in a wierd state
_delay_ms( 50 );
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//scan_resetKeyboard();
// Message
info_print("Keyboard Buffer Flushed");
}
// Main Detection Loop
// The Univac-Sperry F3W9 has a convenient feature, an internal 8 key buffer
// This buffer is only emptied (i.e. sent over the bus) when the REQUEST line is held high
// Because of this, we can utilize the scan_loop to do all of the critical processing,
// without having to resort to interrupts, giving the data reading 100% of the CPU.
// This is because the USB interrupts can wait until the scan_loop is finished to continue.
//
// Normally, this approach isn't taken, as it's easier/faster/safer to use Teensy hardware shift registers
// for serial data transfers.
// However, since the Univac-Sperry F3W9 sends 20 bit packets (including the start bit), the Teensy
// doesn't have a shift register large enough (9 bit max), to hold the data.
// So the line must be polled manually using CPU cycles
//
// Another interesting feature is that there are 2 data lines.
// Output and /Output (NOT'ted version).
// Not really useful here, but could be used for error checking, or eliminating an external NOT gate if
// we were using (but can't...) a hardware decoder like a USART.
inline uint8_t scan_loop()
{
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return 0;
// Protocol Notes:
// - Packets are 20 bits long, including the start bit
// - Each bit is ~105 usecs in length
// - Thus the average packet length is 2.205 msecs
// - Each packet is separated by at least 240 usecs (during a buffer unload)
// - While holding the key down, each packet has a space of about 910 usecs
// - A max of 8 keys can be sent at once (note, the arrow keys seem use 2 packets each, and thus take up twice as much buffer)
// - There is no timing danger for holding the request line, just that data may come in when you don't want it
// Now that the scan loop has been entered, we don't have to worry about interrupts stealing
// precious cycles.
REQUEST_DATA();
// = Delays =
//
// For these calculations to work out properly, then Teensy should be running at 16 MHz
// - 1 bit : 105 usecs is 16 000 000 * 0.000105 = 1680 instructions
// - Bit centering : 52.5 usecs is 16 000 000 * 0.0000525 = 840 instructions
// - Delay : 5 msecs is 16 000 000 * 0.005 = 80 000 instructions
// - Microsecond : 1 usec is 16 000 000 * 0.000001 = 16 instructions
//
// Now, either I can follow these exactly, or based upon the fact that I have >840 tries to find the
// the start bit, and >1680 tries to read the subsequent bits, I have some "flex" time.
// Knowing this, I can make some assumptions that because I'm only reading a total of 20 bits, and will
// be re-centering for each packet.
// This will allow for less worrying about compiler optimizations (and porting!).
// The basic idea is to find a "reliable" value for the start bit, e.g. read it ~10 times.
// Using a for-loop and some addition counters, this should eat up approximately 20-30 instructions per read
// (very loose estimation).
// So reading 10 * 30 instructions = 300 instructions, which is much less than 840 instructions to where the
// bit center is, but is close enough that further delays of ~>1680 instructions will put the next read
// within the next bit period.
// This is all possible because interrupts are disabled at this point, otherwise, all of this reasoning
// would fall apart.
// _delay_us is available to use, fortunately.
// Input Packet Storage (before being processed)
uint16_t incomingPacket[PACKET_STORAGE];
uint8_t numberOfIncomingPackets = 0;
// Sample the data line for ~5 ms, looking for a start bit
// - Sampling every 1 usecs, looking for 10 good samples
// - Accumulated samples will dumped if a high is detected
uint8_t samples = 0;
uint16_t failures = 0;
// Continue waiting for a start bit until MAX_FAILURES has been reached (~5ms of nothing)
while ( failures <= MAX_FAILURES )
{
// Attempt to find the start bit
while ( samples < MAX_SAMPLES )
{
// Delay first
_delay_us( 1 );
// If data is valid, increment
if ( READ_DATA )
{
samples++;
}
// Reset
else
{
samples = 0;
failures++;
// After ~5ms of failures, break the loop
// Each failure is approx 5 instructions + 1 usec, or approximately 1.34 usec)
// So ~3731 failures for ~5ms
// Being exact doesn't matter, as this is just to let the other parts of the
// controller do some processing
if ( failures > MAX_FAILURES )
break;
}
}
// If 10 valid samples of the start bit were obtained,
if ( samples >= MAX_SAMPLES )
{
// Clean out the old packet memory
incomingPacket[numberOfIncomingPackets] = 0;
// Read the next 19 bits into memory (bit 0 is the start bit, which is always 0)
for ( uint8_t c = 1; c < 20; c++ )
{
// Wait until the middle of the next bit
_delay_us( 105 );
// Append the current bit value
incomingPacket[numberOfIncomingPackets] |= (READ_DATA << c);
}
// Packet finished, increment counter
numberOfIncomingPackets++;
}
}
// Stop the keyboard input
STOP_DATA();
// Finished receiving data from keyboard, start packet processing
for ( uint8_t packet = 0; packet < numberOfIncomingPackets; packet++ )
processPacketValue( incomingPacket[packet] );
return 0;
}
// Read in the Packet Data, and decide what to do with it
void processPacketValue( uint16_t packetValue )
{
// = Packet Layout =
//
// A is the first bit received (bit 0), T is the last
//
// | Modifier? | ?? | Scan Code |
// A B C D E F G H I J K L M N O P Q R S T
//
// A - Start bit
// - Always Low
// B -> H - Modifier enabled bits
// - Each bit represents a different modifier "mode"
// - B -> Shift/Lock
// - C -> ??
// - D -> Func
// - E -> ??
// - F -> ??
// - G -> ??
// - H -> ??
// I -> L - ?? No idea yet...
// - The bits change for some combinations, but not pattern has been found yet...
// - I -> ??
// - J -> ??
// - K -> ??
// - L -> ??
// M -> T - Scan Code
// - Bits are organized from low to high (8 bit value)
// - M -> Bit 1
// - N -> Bit 2
// - O -> Bit 3
// - P -> Bit 4
// - Q -> Bit 5
// - R -> Bit 6
// - S -> Bit 7
// - T -> Bit 8
// Separate packet into sections
uint8_t scanCode = (packetValue & 0xFF000) << 12;
uint8_t modifiers = (packetValue & 0x000FE);
uint8_t extra = (packetValue & 0x00F00) << 8;
// Debug Info
char tmpStr1[3];
char tmpStr2[3];
char tmpStr3[3];
hexToStr_op( scanCode, tmpStr1, 2 );
hexToStr_op( modifiers, tmpStr2, 2 );
hexToStr_op( extra, tmpStr3, 2 );
dbug_dPrint( "Scancode: 0x", tmpStr1, " Modifiers: 0x", tmpStr2, " Extra: 0x", tmpStr3 );
dbug_dPrint( "Packet: 0x", tmpStr2, tmpStr3, tmpStr1 );
// TODO List
// - Modifier keys
// - Key Release mechanism
// Compute Modifier keys
// TODO
// Deal with special scan codes
switch ( scanCode )
{
default:
//bufferAdd( scanCode ); TODO - Uncomment when ready for USB output
break;
}
}
// Send data
// NOTE: Does nothing with the Univac-Sperry F3W9
uint8_t scan_sendData( uint8_t dataPayload )
{
return 0;
}
// Signal KeyIndex_Buffer that it has been properly read
inline void scan_finishedWithBuffer( uint8_t sentKeys )
{
return;
}
// Signal that the keys have been properly sent over USB
// TODO
inline void scan_finishedWithUSBBuffer( uint8_t sentKeys )
{
/*
uint8_t foundModifiers = 0;
// Look for all of the modifiers present, there is a max of 8 (but only keys for 5 on the HASCI version)
for ( uint8_t c = 0; c < KeyIndex_BufferUsed; c++ )
{
// The modifier range is from 0x80 to 0x8F (well, the last bit is the ON/OFF signal, but whatever...)
if ( KeyIndex_Buffer[c] <= 0x8F && KeyIndex_Buffer[c] >= 0x80 )
{
// Add the modifier back into the the Key Buffer
KeyIndex_Buffer[foundModifiers] = KeyIndex_Buffer[c];
foundModifiers++;
}
}
// Adjust the size of the new Key Buffer
KeyIndex_BufferUsed = foundModifiers;
*/
}
// Reset/Hold keyboard
// NOTE: Does nothing with the Univac-Sperry F3W9
void scan_lockKeyboard( void )
{
}
// NOTE: Does nothing with the Univac-Sperry F3W9
void scan_unlockKeyboard( void )
{
}
// Reset Keyboard
// - Holds the input read line high to flush the buffer
// - This does not actually reset the keyboard, but always seems brings it to a sane state
// - Won't work fully if keys are being pressed done at the same time
void scan_resetKeyboard( void )
{
// Initiate data request line, but don't read the incoming data
REQUEST_DATA();
// We shouldn't be receiving more than 8 packets (and maybe +1 error signal)
// This is around 22 ms of data, so a delay of 50 ms should be sufficient.
_delay_ms( 50 );
// Stop request line
STOP_DATA();
}