From a7f0732d9e384e39d95c7007cb1f51a133654bad Mon Sep 17 00:00:00 2001
From: Martin Mares <mj@ucw.cz>
Date: Wed, 22 Jul 2020 17:55:21 +0200
Subject: [PATCH] Matrix display & snake

---
 protab/matrix/Makefile |   6 ++
 protab/matrix/matrix.c | 167 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 173 insertions(+)
 create mode 100644 protab/matrix/Makefile
 create mode 100644 protab/matrix/matrix.c

diff --git a/protab/matrix/Makefile b/protab/matrix/Makefile
new file mode 100644
index 0000000..4da665f
--- /dev/null
+++ b/protab/matrix/Makefile
@@ -0,0 +1,6 @@
+ROOT=../..
+BINARY=matrix
+OBJS=matrix.o
+LIB_OBJS=
+
+include $(ROOT)/mk/bluepill.mk
diff --git a/protab/matrix/matrix.c b/protab/matrix/matrix.c
new file mode 100644
index 0000000..b4b368d
--- /dev/null
+++ b/protab/matrix/matrix.c
@@ -0,0 +1,167 @@
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+
+#include <string.h>
+
+typedef unsigned char byte;
+
+static void wait(void)
+{
+	for (int i=0; i<7200; i++)
+		asm volatile ("");
+}
+
+static void set_reg(int reg, int data)
+{
+	data |= reg << 8;
+
+	gpio_clear(GPIOB, GPIO13);
+	wait();
+
+	for (int mask=0x8000; mask; mask >>= 1) {
+		if (data & mask)
+			gpio_set(GPIOB, GPIO12);
+		else
+			gpio_clear(GPIOB, GPIO12);
+		wait();
+		gpio_set(GPIOB, GPIO14);
+		wait();
+		gpio_clear(GPIOB, GPIO14);
+		wait();
+	}
+
+	gpio_set(GPIOB, GPIO13);
+	wait();
+}
+
+byte display[8];
+
+#if 0
+static unsigned char smile[8] = {
+	0x66,	/* .##..##. */
+	0x66,	/* .##..##. */
+	0x00,	/* ........ */
+	0x18,	/* ...##... */
+	0x00,	/* ........ */
+	0xc3,	/* ##....## */
+	0x66,	/* .##..##. */
+	0x3c,	/* ..####.. */
+};
+#endif
+
+static void refresh_display(void)
+{
+	for (int i=1; i<=8; i++)
+		set_reg(i, display[8-i]);
+}
+
+static signed char dirs[4][2] = {{1,0}, {0,-1}, {-1,0}, {0,1}};
+
+static byte snake_dir;
+#define SNAKE_MAX 65
+static byte snake[SNAKE_MAX][2];
+static byte snake_tail, snake_head;
+static byte food[2];
+static unsigned int rng_state = 0xdeadbeef;
+
+static byte buttons[2];
+
+static void gen_food(void)
+{
+	food[0] = (rng_state >> 28) & 7;
+	food[1] = (rng_state >> 20) & 7;
+	rng_state *= 0x3771cadb;
+}
+
+static void snake_init(void)
+{
+	snake[0][0] = 0;
+	snake[0][1] = 0;
+	snake_dir = 3;
+	snake_tail = 0;
+	snake_head = 1;
+	gen_food();
+}
+
+static void snake_show(void)
+{
+	memset(display, 0, 8);
+	for (int i=snake_tail; i != snake_head; i = (i+1) % SNAKE_MAX)
+		display[snake[i][0]] |= 1 << snake[i][1];
+	display[food[0]] |= 1 << food[1];
+	refresh_display();
+}
+
+static void snake_step(void)
+{
+	if (buttons[0])
+		snake_dir = (snake_dir+3) % 4;
+	else if (buttons[1])
+		snake_dir = (snake_dir+1) % 4;
+
+	int hi = (snake_head + SNAKE_MAX - 1) % SNAKE_MAX;
+	int x = snake[hi][0] + dirs[snake_dir][0];
+	int y = snake[hi][1] + dirs[snake_dir][1];
+
+	if (x < 0 || x > 7 || y < 0 || y > 7)
+		return;
+
+	snake[snake_head][0] = x;
+	snake[snake_head][1] = y;
+	snake_head = (snake_head + 1) % SNAKE_MAX;
+
+	if (x == food[0] && y == food[1])
+		gen_food();
+	else
+		snake_tail = (snake_tail + 1) % SNAKE_MAX;
+
+	snake_show();
+}
+
+int main(void)
+{
+	rcc_clock_setup_in_hse_8mhz_out_72mhz();
+	rcc_periph_clock_enable(RCC_GPIOA);
+	rcc_periph_clock_enable(RCC_GPIOB);
+	rcc_periph_clock_enable(RCC_GPIOC);
+
+	// PC13 = BluePill LED
+	gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
+
+	// PB12 = display DIN
+	// PB13 = display CS*
+	// PB14 = display CLK
+	gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_OPENDRAIN, GPIO12 | GPIO13 | GPIO14);
+	gpio_clear(GPIOB, GPIO12);
+	gpio_set(GPIOB, GPIO13);
+	gpio_clear(GPIOB, GPIO14);
+
+	// PA0 = left button
+	// PA1 = right button
+	gpio_set_mode(GPIOA, GPIO_MODE_INPUT, GPIO_CNF_INPUT_PULL_UPDOWN, GPIO0 | GPIO1);
+	gpio_set(GPIOA, GPIO0 | GPIO1);
+
+	refresh_display();
+	set_reg(9, 0);
+	set_reg(10, 0);	// intensity
+	set_reg(11, 7);
+	set_reg(13, 0);	// test
+	set_reg(12, 1);	// shutdown
+
+	snake_init();
+	snake_show();
+
+	for (;;) {
+		buttons[0] = buttons[1] = 0;
+		for (int i=0; i<1000000; i++) {
+			if (!gpio_get(GPIOA, GPIO0))
+				buttons[0] = 1;
+			if (!gpio_get(GPIOA, GPIO1))
+				buttons[1] = 1;
+			asm volatile ("");
+		}
+
+		gpio_toggle(GPIOC, GPIO13);
+		snake_step();
+	}
+}
-- 
2.39.2