From cec47de6ea481731f35c3431727730e7dabfb3bf Mon Sep 17 00:00:00 2001
From: Ain <41307858+nero@users.noreply.github.com>
Date: Sun, 21 Apr 2019 20:08:36 +0000
Subject: [PATCH] Add LPT to serial converter

---
 lpt2ser.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)
 create mode 100644 lpt2ser.c

diff --git a/lpt2ser.c b/lpt2ser.c
new file mode 100644
index 0000000..b87b4e5
--- /dev/null
+++ b/lpt2ser.c
@@ -0,0 +1,55 @@
+#include "drivers/uart_tx.h"
+#include <avr/io.h>
+#include <util/delay.h>
+
+void wait_strobe_on() { // active low
+	while((PIND >> PD2) & 1) {};
+}
+
+void wait_strobe_off() {
+	while(~(PIND >> PD2) & 1) {};
+}
+
+void ack_on() { // active low
+	PORTD &= ~(1 << PD3);
+}
+
+void ack_off() {
+	PORTD |= (1 << PD3);
+}
+
+void busy_on() { // active high
+	PORTB |= (1 << PB4);
+}
+
+void busy_off() {
+	PORTB &= ~(1 << PB4);
+}
+
+int main(void) {
+	// STROBE input is on PD2
+	// PB0-PB3 and PD4-PD7 are data inputs
+	DDRD = (1 << PD3); // ACK output
+	DDRB = (1 << PB4); // BUSY output
+
+	// pull-up per default
+	PORTD |= (1 << PD2) |  (1 << PD3);
+
+	uint8_t i, data;
+
+	for(;;) {
+		wait_strobe_on();
+		data = (PIND & 0xF0) | (PINB & 0x0F);
+		busy_on();
+		ack_on();
+		_delay_us(10); // 5 us minimum
+		ack_off();
+
+		// this blocks until written
+		uart_putc(data);
+
+		busy_off();
+		// make sure we are not reading the same char again
+		wait_strobe_off();
+	}
+}