From 3675419ee36dac85862e7fbe4ab79de8ee2ce65f Mon Sep 17 00:00:00 2001
From: Jeremy Soller <jeremy@system76.com>
Date: Tue, 31 Dec 2019 21:59:04 -0700
Subject: [PATCH] WIP: add parallel port example

---
 src/board/arduino/mega2560/parallel.c | 100 ++++++++++++++++++++++++++
 1 file changed, 100 insertions(+)
 create mode 100644 src/board/arduino/mega2560/parallel.c

diff --git a/src/board/arduino/mega2560/parallel.c b/src/board/arduino/mega2560/parallel.c
new file mode 100644
index 0000000..dfae4ae
--- /dev/null
+++ b/src/board/arduino/mega2560/parallel.c
@@ -0,0 +1,100 @@
+// High resolution pinout can be found here:
+// https://osoyoo.com/wp-content/uploads/2017/08/arduino_mega_2560_pinout.png
+
+#include <stdint.h>
+#include <stdio.h>
+
+#include <arch/gpio.h>
+
+// Mapping of 24-pin ribbon cable to GPIOs
+static struct Gpio gpios[24] = {
+    GPIO(B, 1), GPIO(B, 0),
+    GPIO(B, 3), GPIO(B, 2),
+    GPIO(L, 1), GPIO(L, 0),
+    GPIO(L, 3), GPIO(L, 2),
+    GPIO(L, 5), GPIO(L, 4),
+    GPIO(L, 7), GPIO(L, 6),
+    GPIO(G, 1), GPIO(G, 0),
+    GPIO(D, 7), GPIO(G, 2),
+    GPIO(C, 1), GPIO(C, 0),
+    GPIO(C, 3), GPIO(C, 2),
+    GPIO(C, 5), GPIO(C, 4),
+    GPIO(C, 7), GPIO(C, 6)
+};
+
+struct ParallelPins {
+    // Data (KSO0 - KSO7) - bi-directional
+    uint8_t d0;
+    uint8_t d1;
+    uint8_t d2;
+    uint8_t d3;
+    uint8_t d4;
+    uint8_t d5;
+    uint8_t d6;
+    uint8_t d7;
+    // Wait# (KSO9) - input
+    //  low to indicate cycle may begin, high to indicate cycle may end
+    uint8_t wait_n;
+    // Write# (KSI0) - output
+    //  low to indicate write cycle, high to indicate read cycle
+    uint8_t write_n;
+    // DataStrobe# (KSI1) - output
+    //  low indicates a data cycle
+    uint8_t data_n;
+    // Reset# (KSI2) - output
+    //  low requests device reset
+    uint8_t reset_n;
+    // AddressStrobe# (KSI3) - output
+    //  low indicates an address cycle
+    uint8_t addr_n;
+    // Strap0 (KSI4)
+    //  1K-Ohm pull-down resistor
+    uint8_t strap_0;
+    // Strap1 (KSI5)
+    //  1K-Ohm pull-down resistor
+    uint8_t strap_1;
+};
+
+// Mapping of 24-pin ribbon cable to parallel pins. See schematic
+static struct ParallelPins pins = {
+    .d0 = 1,
+    .d1 = 2,
+    .d2 = 3,
+    .d3 = 7,
+    .d4 = 9,
+    .d5 = 10,
+    .d6 = 13,
+    .d7 = 16,
+    .wait_n = 18,
+    .write_n = 4,
+    .data_n = 5,
+    .reset_n = 6,
+    .addr_n = 8,
+    .strap_0 = 11,
+    .strap_1 = 12,
+};
+
+#define PIN_GPIO(N) \
+    struct Gpio * N = NULL; \
+    if (pins.N > 0 && pins.N < 24) N = &gpios[pins.N - 1]; \
+    if (!N) return; \
+    gpio_set_dir(N, false); \
+    gpio_set(N, false);
+
+void parallel(void) {
+    PIN_GPIO(d0);
+    PIN_GPIO(d1);
+    PIN_GPIO(d2);
+    PIN_GPIO(d3);
+    PIN_GPIO(d4);
+    PIN_GPIO(d5);
+    PIN_GPIO(d6);
+    PIN_GPIO(d7);
+    PIN_GPIO(wait_n);
+    PIN_GPIO(write_n);
+    PIN_GPIO(data_n);
+    PIN_GPIO(reset_n);
+    PIN_GPIO(addr_n);
+    PIN_GPIO(strap_0);
+    PIN_GPIO(strap_1);
+}