From d70239a20314e1c0b96d2a2a19c3435ec77402ed Mon Sep 17 00:00:00 2001
From: Martin Mares <mj@ucw.cz>
Date: Fri, 18 Apr 2025 23:45:38 +0200
Subject: [PATCH] Waiting room: Scanning keyboard

---
 waiting/README          | 16 ++++-----
 waiting/firmware/main.c | 78 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 86 insertions(+), 8 deletions(-)

diff --git a/waiting/README b/waiting/README
index 9c47db3..44c88a9 100644
--- a/waiting/README
+++ b/waiting/README
@@ -14,14 +14,14 @@ I2C2	display 1602: HD44780U controller via PCF8574 expander, needs pull-up to 5V
 BluePill LED		| PC13		 GND |
 			| PC14		  5V |
 			| PC15		 PB9 |
-			| PA0		 PB8 |	TIM4_CH3 - Neopixel data (needs pull-up)
-			| PA1		 PB7 |
-			| PA2		 PB6 |
-			| PA3		 PB5 |
-			| PA4		 PB4 |
-			| PA5		 PB3 |
-			| PA6		PA15 |
-			| PA7		PA12 |
+kbd2 - col 1		| PA0		 PB8 |	TIM4_CH3 - Neopixel data (needs pull-up)
+kbd3 - col 2		| PA1		 PB7 |
+kbd4 - col 3		| PA2		 PB6 |
+kbd5 - col 4		| PA3		 PB5 |
+kbd6 - row 1		| PA4		 PB4 |
+kbd7 - row 2		| PA5		 PB3 |
+kbd8 - row 3		| PA6		PA15 |
+kbd9 - row 4		| PA7		PA12 |
 			| PB0		PA11 |
 			| PB1		PA10 |  RXD1 - debugging console
 I2C2_SCL - display (pu)	| PB10		 PA9 |  TXD1 - debugging console
diff --git a/waiting/firmware/main.c b/waiting/firmware/main.c
index d1f7681..f0c552c 100644
--- a/waiting/firmware/main.c
+++ b/waiting/firmware/main.c
@@ -58,6 +58,11 @@ static void gpio_init(void)
 	gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
 	gpio_clear(GPIOC, GPIO13);
 
+	// PA0-7 = keyboard
+	gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_OPENDRAIN, 0xf0);
+	gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_INPUT_FLOAT, 0x0f);
+	gpio_set(GPIOA, 0xff);
+
 	// PB8 = data for Neopixel
 	gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_OPENDRAIN, GPIO8);
 
@@ -218,6 +223,13 @@ static void display_char(byte ch)
 	display_write_nibble(((ch << 4) & 0xf0) | LCD_BIT_RS);
 }
 
+static void display_hex8(uint x)
+{
+	uint h = (x >> 4) & 0x0f, l = x & 0x0f;
+	display_char('0' + h + (h >= 10 ? 7 : 0));
+	display_char('0' + l + (l >= 10 ? 7 : 0));
+}
+
 static void display_string(const char *str)
 {
 	while (*str)
@@ -268,6 +280,54 @@ static void display_init(void)
 	debug_puts("Display ready\n");
 }
 
+/*** Keyboard ***/
+
+static byte keyboard_step;
+static u16 keyboard_tmp;
+static u16 keyboard_debounce_mask;
+static byte keyboard_debounce_cnt;
+static u16 keyboard_mask;
+static char keyboard_char;
+
+#define KEYBOARD_DEBOUNCE_CYCLES 5
+
+static const char keyboard_map[] = "123A456B789C*0#D";
+
+static void keyboard_scan(void)
+{
+	// The first step does nothing since no row is activated.
+	uint cols = gpio_get(GPIOA, 0x0f) ^ 0x0f;
+	keyboard_tmp |= cols << 4 * keyboard_step;
+
+	if (++keyboard_step == 4) {
+		if (keyboard_tmp == keyboard_debounce_mask) {
+			if (keyboard_debounce_cnt == KEYBOARD_DEBOUNCE_CYCLES) {
+				keyboard_debounce_cnt++;
+				keyboard_mask = keyboard_tmp;
+				if (keyboard_mask && !(keyboard_mask & (keyboard_mask - 1))) {
+					for (uint i=0; i<16; i++)
+						if (keyboard_mask & (1 << i)) {
+							keyboard_char = keyboard_map[i];
+							break;
+						}
+				} else {
+					keyboard_char = 0;
+				}
+			} else if (keyboard_debounce_cnt < KEYBOARD_DEBOUNCE_CYCLES) {
+				keyboard_debounce_cnt++;
+			}
+		} else {
+			keyboard_debounce_mask = keyboard_tmp;
+			keyboard_debounce_cnt = 0;
+		}
+		keyboard_step = 0;
+		keyboard_tmp = 0;
+	}
+
+	gpio_set(GPIOA, 0xf0);
+	gpio_clear(GPIOA, 0x10 << keyboard_step);
+}
+
 /*** Neopixels ***/
 
 #if 0
@@ -571,8 +631,26 @@ int main(void)
 
 	u32 last_blink = 0;
 	// u32 last_send = 0;
+	uint key_column = 0;
 
 	for (;;) {
+		keyboard_scan();
+#if 0
+		if (keyboard_mask != last_key_mask) {
+			last_key_mask = keyboard_mask;
+			display_goto(1, 0);
+			display_hex8((keyboard_mask >> 8) & 0xff);
+			display_hex8(keyboard_mask & 0xff);
+		}
+#endif
+		if (keyboard_char) {
+			if (key_column < 15) {
+				display_goto(1, key_column++);
+				display_char(keyboard_char);
+			}
+			keyboard_char = 0;
+		}
+
 		if (ms_ticks - last_blink >= 300) {
 			debug_led_toggle();
 			last_blink = ms_ticks;
-- 
2.47.3