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| 1 | +;---------------------------------------------------------------------------; |
| 2 | +; Software implemented UART module ; |
| 3 | +; (C)ChaN, 2005 (http://elm-chan.org/) ; |
| 4 | +;---------------------------------------------------------------------------; |
| 5 | +; Bit rate settings: |
| 6 | +; |
| 7 | +; 1MHz 2MHz 4MHz 6MHz 8MHz 10MHz 12MHz 16MHz 20MHz |
| 8 | +; 2.4kbps 138 - - - - - - - - |
| 9 | +; 4.8kbps 68 138 - - - - - - - |
| 10 | +; 9.6kbps 33 68 138 208 - - - - - |
| 11 | +; 19.2kbps - 33 68 102 138 173 208 - - |
| 12 | +; 38.4kbps - - 33 50 68 85 102 138 172 |
| 13 | +; 57.6kbps - - 21 33 44 56 68 91 114 |
| 14 | +; 115.2kbps - - - - 21 27 33 44 56 |
| 15 | + |
| 16 | +.nolist |
| 17 | +#include <avr/io.h> |
| 18 | +.list |
| 19 | + |
| 20 | +#define BPS 44 /* Bit delay. (see above table) */ |
| 21 | +#define BIDIR 0 /* 0:Separated Tx/Rx, 1:Shared Tx/Rx */ |
| 22 | + |
| 23 | +#define OUT_1 sbi _SFR_IO_ADDR(SUART_OUT_PORT), SUART_OUT_BIT /* Output 1 */ |
| 24 | +#define OUT_0 cbi _SFR_IO_ADDR(SUART_OUT_PORT), SUART_OUT_BIT /* Output 0 */ |
| 25 | +#define SKIP_IN_1 sbis _SFR_IO_ADDR(SUART_IN_PIN), SUART_IN_BIT /* Skip if 1 */ |
| 26 | +#define SKIP_IN_0 sbic _SFR_IO_ADDR(SUART_IN_PIN), SUART_IN_BIT /* Skip if 0 */ |
| 27 | + |
| 28 | + |
| 29 | + |
| 30 | +#ifdef SPM_PAGESIZE |
| 31 | +.macro _LPMI reg |
| 32 | + lpm \reg, Z+ |
| 33 | +.endm |
| 34 | +.macro _MOVW dh,dl, sh,sl |
| 35 | + movw \dl, \sl |
| 36 | +.endm |
| 37 | +#else |
| 38 | +.macro _LPMI reg |
| 39 | + lpm |
| 40 | + mov \reg, r0 |
| 41 | + adiw ZL, 1 |
| 42 | +.endm |
| 43 | +.macro _MOVW dh,dl, sh,sl |
| 44 | + mov \dl, \sl |
| 45 | + mov \dh, \sh |
| 46 | +.endm |
| 47 | +#endif |
| 48 | + |
| 49 | + |
| 50 | + |
| 51 | +;---------------------------------------------------------------------------; |
| 52 | +; Transmit a byte in serial format of N81 |
| 53 | +; |
| 54 | +;Prototype: void xmit (uint8_t data); |
| 55 | +;Size: 16 words |
| 56 | + |
| 57 | +.global xmit |
| 58 | +.func xmit |
| 59 | +xmit: |
| 60 | +#if BIDIR |
| 61 | + ldi r23, BPS-1 ;Pre-idle time for bidirectional data line |
| 62 | +5: dec r23 ; |
| 63 | + brne 5b ;/ |
| 64 | +#endif |
| 65 | + in r0, _SFR_IO_ADDR(SREG) ;Save flags |
| 66 | + |
| 67 | + com r24 ;C = start bit |
| 68 | + ldi r25, 10 ;Bit counter |
| 69 | + cli ;Start critical section |
| 70 | + |
| 71 | +1: ldi r23, BPS-1 ;----- Bit transferring loop |
| 72 | +2: dec r23 ;Wait for a bit time |
| 73 | + brne 2b ;/ |
| 74 | + brcs 3f ;MISO = bit to be sent |
| 75 | + OUT_1 ; |
| 76 | +3: brcc 4f ; |
| 77 | + OUT_0 ;/ |
| 78 | +4: lsr r24 ;Get next bit into C |
| 79 | + dec r25 ;All bits sent? |
| 80 | + brne 1b ; no, coutinue |
| 81 | + |
| 82 | + out _SFR_IO_ADDR(SREG), r0 ;End of critical section |
| 83 | + ret |
| 84 | +.endfunc |
| 85 | + |
| 86 | + |
| 87 | + |
| 88 | +;---------------------------------------------------------------------------; |
| 89 | +; Receive a byte |
| 90 | +; |
| 91 | +;Prototype: uint8_t rcvr (void); |
| 92 | +;Size: 19 words |
| 93 | + |
| 94 | +.global rcvr |
| 95 | +.func rcvr |
| 96 | +rcvr: |
| 97 | + in r0, _SFR_IO_ADDR(SREG) ;Save flags |
| 98 | + |
| 99 | + ldi r24, 0x80 ;Receiving shift reg |
| 100 | + cli ;Start critical section |
| 101 | + |
| 102 | +1: SKIP_IN_1 ;Wait for idle |
| 103 | + rjmp 1b |
| 104 | +2: SKIP_IN_0 ;Wait for start bit |
| 105 | + rjmp 2b |
| 106 | + ldi r25, BPS/2 ;Wait for half bit time |
| 107 | +3: dec r25 |
| 108 | + brne 3b |
| 109 | + |
| 110 | +4: ldi r25, BPS ;----- Bit receiving loop |
| 111 | +5: dec r25 ;Wait for a bit time |
| 112 | + brne 5b ;/ |
| 113 | + lsr r24 ;Next bit |
| 114 | + SKIP_IN_0 ;Get a data bit into r24.7 |
| 115 | + ori r24, 0x80 |
| 116 | + brcc 4b ;All bits received? no, continue |
| 117 | + |
| 118 | + out _SFR_IO_ADDR(SREG), r0 ;End of critical section |
| 119 | + ret |
| 120 | +.endfunc |
| 121 | + |
| 122 | + |
| 123 | +; Not wait for start bit. This should be called after detecting start bit. |
| 124 | +.global recv |
| 125 | +.func recv |
| 126 | +recv: |
| 127 | + in r0, _SFR_IO_ADDR(SREG) ;Save flags |
| 128 | + |
| 129 | + ldi r24, 0x80 ;Receiving shift reg |
| 130 | + cli ;Start critical section |
| 131 | + |
| 132 | +;1: SKIP_IN_1 ;Wait for idle |
| 133 | +; rjmp 1b |
| 134 | +;2: SKIP_IN_0 ;Wait for start bit |
| 135 | +; rjmp 2b |
| 136 | + ldi r25, BPS/2 ;Wait for half bit time |
| 137 | +3: dec r25 |
| 138 | + brne 3b |
| 139 | + |
| 140 | +4: ldi r25, BPS ;----- Bit receiving loop |
| 141 | +5: dec r25 ;Wait for a bit time |
| 142 | + brne 5b ;/ |
| 143 | + lsr r24 ;Next bit |
| 144 | + SKIP_IN_0 ;Get a data bit into r24.7 |
| 145 | + ori r24, 0x80 |
| 146 | + brcc 4b ;All bits received? no, continue |
| 147 | + |
| 148 | + ldi r25, BPS/2 ;Wait for half bit time |
| 149 | +6: dec r25 |
| 150 | + brne 6b |
| 151 | +7: SKIP_IN_1 ;Wait for stop bit |
| 152 | + rjmp 7b |
| 153 | + |
| 154 | + out _SFR_IO_ADDR(SREG), r0 ;End of critical section |
| 155 | + ret |
| 156 | +.endfunc |
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