1 | #include "main.h"
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2 | #include "suart.h"
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3 |
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4 |
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5 |
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6 | #define BIT_TIME (u8)((XTAL / BAUD) / PRESCALE)
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7 |
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8 |
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9 | volatile u8 stx_count;
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10 | u8 stx_data;
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11 |
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12 | volatile u8 srx_done;
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13 | u8 srx_data;
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14 | u8 srx_mask;
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15 | u8 srx_tmp;
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16 |
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17 |
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18 | void suart_init( void )
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19 | {
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20 | SBIT(PORTD,STX) = 1;
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21 | // OCR0A = TCNT0 + 1; // force first compare
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22 | // TCCR0A = 0; // Default: Normal port operation
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23 | TCCR0B = 1 << CS01 | 1<<CS00; // clk/64
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24 | // TIFR0 = 1<<ICF1; // clear pending interrupt
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25 | TIMSK0 = 1 << OCIE0A; // enable output compare interrupt
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26 |
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27 | EICRA = 1 << ISC01; // falling edge
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28 | EIMSK = 1 << INT0; // enable edge interrupt
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29 |
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30 | stx_count = 0; // nothing to sent
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31 | srx_done = 0; // nothing received
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32 | STXDDR |= 1 << STX; // TX output
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33 | }
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34 |
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35 |
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36 | u8 sgetchar (void) // get byte
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37 | {
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38 | while (!srx_done); // wait until byte received
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39 | srx_done = 0;
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40 | return srx_data;
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41 | }
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42 |
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43 |
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44 | ISR (INT0_vect) // rx start
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45 | {
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46 | OCR0B = TCNT0 + (u8)((BIT_TIME * 3) / 2);// scan 1.5 bits after start
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47 |
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48 | srx_tmp = 0; // clear bit storage
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49 | srx_mask = 1; // bit mask
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50 | EIMSK &= ~(1 << INT0); // disable edge interrupt
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51 | //if( !(SRXPIN & 1<<SRX)) // still low
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52 | TIMSK0 = 1<<OCIE0A^1<<OCIE0B; // wait for first bit
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53 | TIFR0 = 1<<OCF0B; // clear pending interrupt ? why does that output compare int occur?
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54 | // EIFR &= ~(1 << INTF0); // clear any pending edge interrupt
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55 | }
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56 |
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57 |
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58 | ISR (TIMER0_COMPB_vect)
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59 | {
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60 | u8 in = SRXPIN; // scan rx line
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61 | PORTB = 0x00;
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62 | if (srx_mask) {
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63 | if (in & 1 << SRX)
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64 | srx_tmp |= srx_mask;
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65 | srx_mask <<= 1;
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66 | OCR0B += BIT_TIME; // next bit slice
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67 | } else {
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68 | srx_done = 1; // mark rx data valid
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69 | srx_data = srx_tmp; // store rx data
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70 | // TIFR0 = 1<<ICF1; // clear pending interrupt
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71 | TIMSK0 = 1<<OCIE0A; // enable tx and wait for start
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72 | EIMSK = 1 << INT0; // reenable edge interrupt
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73 |
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74 | }
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75 | PORTB = 0x02;
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76 | }
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77 |
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78 |
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79 | void sputchar (u8 val) // send byte
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80 | {
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81 | while (stx_count); // until last byte finished
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82 | stx_data = ~val; // invert data for Stop bit generation
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83 | stx_count = 10; // 10 bits: Start + data + Stop
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84 | }
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85 |
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86 |
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87 | void sputs (u8 *txt) // send string
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88 | {
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89 | while (*txt)
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90 | sputchar (*txt++);
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91 | }
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92 |
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93 |
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94 | ISR (TIMER0_COMPA_vect) // tx bit
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95 | {
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96 | u8 dout;
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97 | u8 count;
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98 |
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99 | OCR0A += BIT_TIME; // next bit slice
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100 | count = stx_count;
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101 |
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102 | if (count) {
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103 | stx_count = --count; // count down
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104 | // ??? dout = 1<<COM0A1; // set low on next compare
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105 | dout = 0;
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106 | if (count != 9) { // no start bit
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107 | if (!(stx_data & 1)) // test inverted data
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108 | //??? dout = 1<<COM0A1^1<<COM0A0; // set high on next compare
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109 | dout = 1;
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110 | stx_data >>= 1; // shift zero in from left
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111 | }
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112 | // TCCR0A = dout;
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113 | // STX = (dout == 0) ? 1 : 0;
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114 | SBIT(PORTD,STX) = dout;
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115 | }
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116 | }
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