// One way communication from ATMEGA8 to host PC through SCK and MISO
// lines without any addiontional hardware support on the ATMEL side,
// and no device drivers on the host PC side.
//
// Why
//   No additional soldering needed to get (debugging) output,
//   since it uses the same lines as the ISP parallel programmer.
//
// On the ATMEL side:
//   - uses a polling loop which monitors the clock (SCK)
//   - uses MISO to send the data bit by bit
//   - continues after a timeout if no one is listening on the other
//     side.
// On the host PC side:
//   - uses the parallel port (could be extended though)
//   - uses SCK to drive the clock to indicate the ATMEL we're ready
//     to receive the next bit.
//
// The speed is dependant on the speed the host PC toggles the clock
// and whether the ATMEL can keep up. When the ATMEL runs at 1Mhz, I
// get to ~100kbaud with some errors.
//
// TODO
//   - make communication bi-directional instead of only from
//     ATMEL to host PC using MOSI. Easy to do, just use MOSI also.
//   - add parity for error detection?
//   - make CPU configurable by making location of SCK/MISO pins
//     configurable.
//   - Use SPI protocol instead?
//
// (c)2005 R. Nijlunsing <address@hidden>
// License: LGPL (see http://www.gnu.org/copyleft/lesser.html)

#include <avr/io.h>
#include <inttypes.h>

// All functions are defined extern to make them easy to include in a
// library. However, for optimisations like skip-unused-functions use
// one source file like 'main.c' which includes:
//    #define extern static
//    #include "msio.c"
// ..and compile with something like:
//    gcc -finline-functions -funit-at-a-time main.c

// See msio.c for explanation of functions.
extern void msioInit(void);
extern uint8_t msioSendByte(uint8_t s);
extern uint8_t msioSendString(char *buffer);
extern uint8_t msioSendUINT8_T(char *fmt, uint8_t val);