144 lines
2.5 KiB
C
144 lines
2.5 KiB
C
#include <avr/io.h>
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#include <avr/interrupt.h>
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#include <avr/sleep.h>
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#include <tabby/printer.h>
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#include <tabby/avr/uart.h>
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static volatile tabby_printer_packet header = {
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.type = 0,
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.compression = 0,
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.size = 0
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};
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static volatile uint16_t i = 0,
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b = 0;
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/*
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* SPI byte receipt interrupt vector
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*/
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ISR(SPI_STC_vect) {
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uint8_t in = SPDR,
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out = 0x00;
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uart_putchar(in, NULL);
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switch (i) {
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case 0: {
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if (in == 0x88) {
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header.data[0] = in;
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i++;
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b = 0;
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}
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break;
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}
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case 1: {
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if (in == 0x33) {
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header.data[1] = in;
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i++;
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} else {
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i = 0;
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}
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break;
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}
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case 2: {
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header.type = in;
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i++;
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break;
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}
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case 3: {
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header.compression = in;
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i++;
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break;
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}
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case 4: {
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header.size = in;
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i++;
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break;
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}
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case 5: {
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header.size |= in << 8;
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i++;
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break;
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}
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default: {
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if (b <= header.size) {
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b++;
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} else if (b == header.size + 1) {
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b++;
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out = 0x81;
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} else if (b == header.size + 2) {
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b++;
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} else if (b == header.size + 3) {
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i = 0;
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}
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}
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}
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SPDR = out;
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}
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static void setup_clock_external() {
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/*
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* Configure MISO as output
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*/
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DDRB |= (1 << DDB4);
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/*
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* Configure SS as input
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*/
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DDRB &= ~(1 << DDB2);
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/*
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* Set SPI slave mode, and shift in/out most significant bit first
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*/
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SPCR &= ~((1 << MSTR) | (1 << DORD));
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/*
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* Enable SPI in Mode 3 with interrupts
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*/
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SPCR |= (1 << CPOL) | (1 << CPHA) | (1 << SPIE) | (1 << SPE);
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/*
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* Initialize the SPI Data Register and serial buffer
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*/
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SPDR = 0;
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}
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int main() {
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/*
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* Best turn on the serial UART!
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*/
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uart_init();
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/*
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* By default, the Game Boy link port is configured to monitor for external
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* clock pulses, so we'll go ahead and do that in this case.
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*/
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setup_clock_external();
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/*
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* We do actually want to globally enable interrupts here, so here's that
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* one assembly instruction to do so.
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*/
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sei();
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while (1) {
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sleep_mode();
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}
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return 0;
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}
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