firmware/s88w-t.c

   1 /* $Id$
   2
   3 This file is part of the MSP Märklin suite
   4 Copyright © 2010  Mikkosoft Productions, Mikko Rasa
   5 Distributed under the GPL
   6
   7 Firmware for wireless S88 transmitter module
   8
   9 ATMega pinout:
  10 D0 - serial RX
  11 D1 - serial TX
  12 D2 - input 1
  13 D3 - input 2
  14 D4 - input 3
  15 D5 - input 4
  16 D6 - input 5
  17 D7 - input 6
  18 B0 - input 7
  19 B1 - input 8
  20
  21 Inputs are pulled high by internal pull-up resistors.  Connect to GND to
  22 activate.
  23 */
  24
  25 #include <avr/io.h>
  26 #include <avr/interrupt.h>
  27
  28 #define BIT(n) (1<<(n))
  29
  30 void send_state(void);
  31 void write_serial(uint8_t);
  32 uint8_t hexdigit(uint8_t);
  33
  34 volatile uint8_t state = 0;
  35
  36 int main()
  37 {
  38         DDRD = 0x02;   // 00000010
  39         PORTD = 0xFC;  // 11111100
  40         DDRB = 0x20;   // 00100000
  41         PORTB = 0x3F;  // 00111111
  42
  43         // 9600 baud, 8N1
  44         UBRR0H = 0;
  45         UBRR0L = 103;
  46         UCSR0C = BIT(UCSZ00) | BIT(UCSZ01);
  47         UCSR0B = BIT(RXEN0) | BIT(TXEN0);
  48
  49         // 0.5 Hz (CK/1024, TOP=31250)
  50         TCCR1A = 0;
  51         TCCR1B = BIT(WGM12) | BIT(CS12) | BIT(CS10);
  52         OCR1AH = 122;
  53         OCR1AL = 18;
  54         TIMSK1 = BIT(OCIE1A);
  55
  56         sei();
  57
  58         while(1)
  59         {
  60                 uint8_t i;
  61                 uint8_t input = 0;
  62                 uint8_t valid = 0xFF;
  63
  64                 for(i=0; i<100; ++i)
  65                 {
  66                         uint8_t pins;
  67
  68                         pins = ~((PIND>>2) | (PINB<<6));
  69                         if(i==0)
  70                                 input = pins;
  71                         valid &= ~(pins^input);
  72                 }
  73
  74                 input &= valid;
  75                 input |= state&~valid;
  76
  77                 if(input!=state)
  78                 {
  79                         state = input;
  80                         send_state();
  81                 }
  82         }
  83
  84         return 0;
  85 }
  86
  87 ISR(TIMER1_COMPA_vect)
  88 {
  89         send_state();
  90 }
  91
  92 void send_state(void)
  93 {
  94         write_serial(':');
  95         write_serial(hexdigit(state>>4));
  96         write_serial(hexdigit(state&0xF));
  97 }
  98
  99 void write_serial(uint8_t c)
 100 {
 101         while(!(UCSR0A&(1<<UDRE0))) ;
 102         UDR0 = c;
 103 }
 104
 105 uint8_t hexdigit(uint8_t n)
 106 {
 107         if(n<10)
 108                 return '0'+n;
 109         else
 110                 return 'A'+(n-0xA);
 111 }