1 /*

     2  * DMX output.

     3  *

     4  * See doc/dmx.txt for the RX-485 bus protocol details...

     5  */

     6 

     7 #include <avr/io.h>

     8 #include <util/delay.h>

     9 

    10 #include "stdlib.h"

    11 

    12 // debug

    13 #define DEBUG_DDR   DDRB

    14 #define DEBUG_PORT  PORTB

    15 #define DEBUG_LED   0

    16 

    17 void led_init ()

    18 {

    19     sbi(&DEBUG_DDR, DEBUG_LED);

    20 }

    21 

    22 void led_on ()

    23 {

    24     sbi(&DEBUG_PORT, DEBUG_LED);

    25 }

    26 

    27 void led_off ()

    28 {

    29     cbi(&DEBUG_PORT, DEBUG_LED);

    30 }

    31 

    32 void led_toggle ()

    33 {

    34     xbi(&DEBUG_PORT, DEBUG_LED);

    35 }

    36 

    37 // DMX

    38 #define DMX_DDR     DDRB

    39 #define DMX_PORT    PORTB

    40 #define DMX_DATA    3       // SPI MOSI

    41 

    42 // baud rate: 250k = 4µs / bit

    43 #define DMX_BAUD    (250 * 1000)

    44 #define DMX_US      4

    45 

    46 // CPU cycles / bit: 64 @ 16Mhz

    47 #define DMX_CYCLES  (F_CPU / DMX_BAUD)

    48 

    49 void dmx_init ()

    50 {

    51     // dmx data out: idle (high)

    52     sbi(&DMX_PORT, DMX_DATA);

    53     sbi(&DMX_DDR, DMX_DATA);

    54 }

    55 

    56 static inline void dmx_high ()

    57 {

    58     sbi(&DMX_PORT, DMX_DATA);

    59 }

    60 

    61 static inline void dmx_low ()

    62 {

    63     cbi(&DMX_PORT, DMX_DATA);

    64 }

    65 

    66 #define dmx_pause(bits) _delay_us((DMX_US * bits))

    67 

    68 static void dmx_break ()

    69 {

    70     // break

    71     dmx_low();

    72     dmx_pause(22);

    73 

    74     // mark-after-break (MAB)

    75     dmx_high();

    76     dmx_pause(2);

    77 }

    78 

    79 #include "dmx_frame.c"

    80 

    81 static void dmx_packet (byte r, byte g, byte b)

    82 {

    83     dmx_break();

    84     dmx_frame(0);

    85 

    86     dmx_frame(0);       // control

    87     dmx_frame(r);

    88     dmx_frame(g);

    89     dmx_frame(b);

    90     dmx_frame(0);       // madness

    91 }

    92 

    93 void main ()

    94 {

    95     led_init();

    96     dmx_init();

    97 

    98     // dmx

    99     while (true) {

   100         dmx_packet(0x00, 0x00, 0xff);

   101         dmx_pause(100);

   102 

   103         led_toggle();

   104     }

   105 }