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Ensure clock pulses occur at ~8192Hz

Browse source 
Other changes:

    * Rip out checksum routine; it's a lot better to rely on the Game Boy
      Printer returning the device identifier and status bitfield to
      resend packets when checksum error bit is set

    * Ensure incoming value is read just ahead of rising edge (but I was
      already doing that so like yeah)

    * Ensure 270µs interval after packet transmission
This commit is contained in:
XANTRONIX Development 2016-06-04 23:58:07 -05:00
parent 49463eb8f8
commit fa4b6ae020
2 changed files with 9 additions and 28 deletions
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2
avr/Makefile
View file

@ -8,7 +8,7 @@ CROSS = avr-
CC = $(CROSS)gcc
CFLAGS = $(CGFLAGS) -Wall -Os -mmcu=atmega328p -I$(INCLUDE_PATH) \
-DF_CPU=$(CLOCK_SPEED)
-DF_CPU=$(CLOCK_SPEED) -DUSE_2X
LDFLAGS =
OBJCOPY = $(CROSS)objcopy

35
avr/send.c
View file

@ -68,10 +68,10 @@ static uint8_t spi_send_byte(uint8_t value) {
PORTB &= ~(1 << PORTB4);
}
value <<= 1;
ret <<= 1;
_delay_us(61);
_delay_us(60);
ret <<= 1;
value <<= 1;
if (PINB & (1 << PINB3)) {
ret |= 1;
@ -79,11 +79,9 @@ static uint8_t spi_send_byte(uint8_t value) {
PORTB |= (1 << PORTB5);
_delay_us(60);
_delay_us(61);
}
_delay_us(150);
return ret;
}
@ -104,22 +102,7 @@ static void spi_send_packet() {
response.device = spi_send_byte(0);
response.status = spi_send_byte(0);
_delay_us(270);
}
static uint16_t checksum() {
uint16_t sum = 0;
size_t i;
for (i=2; i<6; i++) {
sum += header.data[i];
}
for (i=0; i<header.size; i++) {
sum += body[i];
}
return sum;
_delay_us(244);
}
int main() {
@ -224,12 +207,10 @@ int main() {
i = 0;
b = 0;
if (sum == checksum()) {
spi_send_packet();
spi_send_packet();
uart_putchar(response.device, NULL);
uart_putchar(response.status, NULL);
}
uart_putchar(response.device, NULL);
uart_putchar(response.status, NULL);
}
}
}