+/* 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
+ REQUEST_DDR |= (1 << REQUEST_PIN); // Set to output
+ STOP_DATA(); // Set the line high to stop incoming data
+
+ // Reset the keyboard before scanning, we might be in a wierd state
+ _delay_ms( 50 );
+ scan_resetKeyboard();
+}
+
+
+// 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()
+{
+ // 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( void )
+{
+ return;
+}
+
+// Signal that the keys have been properly sent over USB
+// TODO
+inline void scan_finishedWithUSBBuffer( void )
+{
+ /*
+ 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();
+}
+