diff options
Diffstat (limited to 'keyboard/hhkb/rn42/suart.S')
| -rw-r--r-- | keyboard/hhkb/rn42/suart.S | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/keyboard/hhkb/rn42/suart.S b/keyboard/hhkb/rn42/suart.S new file mode 100644 index 0000000000..9fa5452928 --- /dev/null +++ b/keyboard/hhkb/rn42/suart.S @@ -0,0 +1,156 @@ +;---------------------------------------------------------------------------;
+; Software implemented UART module ;
+; (C)ChaN, 2005 (http://elm-chan.org/) ;
+;---------------------------------------------------------------------------;
+; Bit rate settings:
+;
+; 1MHz 2MHz 4MHz 6MHz 8MHz 10MHz 12MHz 16MHz 20MHz
+; 2.4kbps 138 - - - - - - - -
+; 4.8kbps 68 138 - - - - - - -
+; 9.6kbps 33 68 138 208 - - - - -
+; 19.2kbps - 33 68 102 138 173 208 - -
+; 38.4kbps - - 33 50 68 85 102 138 172
+; 57.6kbps - - 21 33 44 56 68 91 114
+; 115.2kbps - - - - 21 27 33 44 56
+
+.nolist
+#include <avr/io.h>
+.list
+
+#define BPS 44 /* Bit delay. (see above table) */
+#define BIDIR 0 /* 0:Separated Tx/Rx, 1:Shared Tx/Rx */
+
+#define OUT_1 sbi _SFR_IO_ADDR(SUART_OUT_PORT), SUART_OUT_BIT /* Output 1 */
+#define OUT_0 cbi _SFR_IO_ADDR(SUART_OUT_PORT), SUART_OUT_BIT /* Output 0 */
+#define SKIP_IN_1 sbis _SFR_IO_ADDR(SUART_IN_PIN), SUART_IN_BIT /* Skip if 1 */
+#define SKIP_IN_0 sbic _SFR_IO_ADDR(SUART_IN_PIN), SUART_IN_BIT /* Skip if 0 */
+
+
+
+#ifdef SPM_PAGESIZE
+.macro _LPMI reg
+ lpm \reg, Z+
+.endm
+.macro _MOVW dh,dl, sh,sl
+ movw \dl, \sl
+.endm
+#else
+.macro _LPMI reg
+ lpm
+ mov \reg, r0
+ adiw ZL, 1
+.endm
+.macro _MOVW dh,dl, sh,sl
+ mov \dl, \sl
+ mov \dh, \sh
+.endm
+#endif
+
+
+
+;---------------------------------------------------------------------------;
+; Transmit a byte in serial format of N81
+;
+;Prototype: void xmit (uint8_t data);
+;Size: 16 words
+
+.global xmit
+.func xmit
+xmit:
+#if BIDIR
+ ldi r23, BPS-1 ;Pre-idle time for bidirectional data line
+5: dec r23 ;
+ brne 5b ;/
+#endif
+ in r0, _SFR_IO_ADDR(SREG) ;Save flags
+
+ com r24 ;C = start bit
+ ldi r25, 10 ;Bit counter
+ cli ;Start critical section
+
+1: ldi r23, BPS-1 ;----- Bit transferring loop
+2: dec r23 ;Wait for a bit time
+ brne 2b ;/
+ brcs 3f ;MISO = bit to be sent
+ OUT_1 ;
+3: brcc 4f ;
+ OUT_0 ;/
+4: lsr r24 ;Get next bit into C
+ dec r25 ;All bits sent?
+ brne 1b ; no, coutinue
+
+ out _SFR_IO_ADDR(SREG), r0 ;End of critical section
+ ret
+.endfunc
+
+
+
+;---------------------------------------------------------------------------;
+; Receive a byte
+;
+;Prototype: uint8_t rcvr (void);
+;Size: 19 words
+
+.global rcvr
+.func rcvr
+rcvr:
+ in r0, _SFR_IO_ADDR(SREG) ;Save flags
+
+ ldi r24, 0x80 ;Receiving shift reg
+ cli ;Start critical section
+
+1: SKIP_IN_1 ;Wait for idle
+ rjmp 1b
+2: SKIP_IN_0 ;Wait for start bit
+ rjmp 2b
+ ldi r25, BPS/2 ;Wait for half bit time
+3: dec r25
+ brne 3b
+
+4: ldi r25, BPS ;----- Bit receiving loop
+5: dec r25 ;Wait for a bit time
+ brne 5b ;/
+ lsr r24 ;Next bit
+ SKIP_IN_0 ;Get a data bit into r24.7
+ ori r24, 0x80
+ brcc 4b ;All bits received? no, continue
+
+ out _SFR_IO_ADDR(SREG), r0 ;End of critical section
+ ret
+.endfunc
+
+
+; Not wait for start bit. This should be called after detecting start bit.
+.global recv
+.func recv
+recv:
+ in r0, _SFR_IO_ADDR(SREG) ;Save flags
+
+ ldi r24, 0x80 ;Receiving shift reg
+ cli ;Start critical section
+
+;1: SKIP_IN_1 ;Wait for idle
+; rjmp 1b
+;2: SKIP_IN_0 ;Wait for start bit
+; rjmp 2b
+ ldi r25, BPS/2 ;Wait for half bit time
+3: dec r25
+ brne 3b
+
+4: ldi r25, BPS ;----- Bit receiving loop
+5: dec r25 ;Wait for a bit time
+ brne 5b ;/
+ lsr r24 ;Next bit
+ SKIP_IN_0 ;Get a data bit into r24.7
+ ori r24, 0x80
+ brcc 4b ;All bits received? no, continue
+
+ ldi r25, BPS/2 ;Wait for half bit time
+6: dec r25
+ brne 6b
+7: SKIP_IN_1 ;Wait for stop bit
+ rjmp 7b
+
+ out _SFR_IO_ADDR(SREG), r0 ;End of critical section
+ ret
+.endfunc
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