terom@62: /*
terom@62:  * Per-frame timing-critical bit-banging.
terom@62:  *
terom@62:  * Shamelessly stolen from
terom@62:  *  http://code.google.com/p/tinkerit/source/browse/trunk/DmxSimple/DmxSimple.cpp
terom@62:  *
terom@62:  *  Copyright (c) 2008-2009 Peter Knight, Tinker.it!
terom@62:  *
terom@62:  * Consumes approx. 11 * 64 ~= 705 clock cycles
terom@62:  * Leaves the line idle (high) on return.
terom@62:  */
terom@62: void dmx_frame (volatile byte value)
terom@62: {
terom@62:   uint8_t bitCount, delCount;
terom@62:   __asm__ volatile (
terom@62:     "cli\n"
terom@62:     "ld __tmp_reg__,%a[dmxPort]\n"
terom@62:     "and __tmp_reg__,%[outMask]\n"
terom@62:     "st %a[dmxPort],__tmp_reg__\n"
terom@62:     "ldi %[bitCount],11\n" // 11 bit intervals per transmitted byte
terom@62:     "rjmp bitLoop%=\n"     // Delay 2 clock cycles.
terom@62:   "bitLoop%=:\n"\
terom@62:     "ldi %[delCount],%[delCountVal]\n"
terom@62:   "delLoop%=:\n"
terom@62:     "nop\n"
terom@62:     "dec %[delCount]\n"
terom@62:     "brne delLoop%=\n"
terom@62:     "ld __tmp_reg__,%a[dmxPort]\n"
terom@62:     "and __tmp_reg__,%[outMask]\n"
terom@62:     "sec\n"
terom@62:     "ror %[value]\n"
terom@62:     "brcc sendzero%=\n"
terom@62:     "or __tmp_reg__,%[outBit]\n"
terom@62:   "sendzero%=:\n"
terom@62:     "st %a[dmxPort],__tmp_reg__\n"
terom@62:     "dec %[bitCount]\n"
terom@62:     "brne bitLoop%=\n"
terom@62:     "sei\n"
terom@62:     :
terom@62:       [bitCount] "=&d" (bitCount),
terom@62:       [delCount] "=&d" (delCount)
terom@62:     :
terom@62:       [dmxPort] "e" (&DMX_PORT),
terom@62:       [outMask] "r" (~(1 << DMX_DATA)),
terom@62:       [outBit] "r" ((1 << DMX_DATA)),
terom@62:       [delCountVal] "M" (F_CPU/1000000-3),
terom@62:       [value] "r" (value)
terom@62:   );
terom@62: }