From e85611736cc052d064a0b9d4387a2d5bf4d3a82e Mon Sep 17 00:00:00 2001
From: Jeremy Soller <jeremy@system76.com>
Date: Sat, 7 Dec 2019 11:02:02 -0700
Subject: [PATCH] Debounce key releases (needs testing)

---
 src/board/system76/galp3-c/kbscan.c | 33 +++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/src/board/system76/galp3-c/kbscan.c b/src/board/system76/galp3-c/kbscan.c
index 57e3889..1bb200e 100644
--- a/src/board/system76/galp3-c/kbscan.c
+++ b/src/board/system76/galp3-c/kbscan.c
@@ -1,3 +1,5 @@
+#include <mcs51/8052.h>
+
 #include <arch/delay.h>
 #include <board/kbc.h>
 #include <board/kbscan.h>
@@ -18,6 +20,9 @@ void kbscan_init(void) {
     KSOLGOEN = 0;
     KSOHGCTRL = 0xFF;
     KSOHGOEN = 0;
+
+    // Make sure timer 2 is stopped
+    T2CON = 0;
 }
 
 void kbscan_event(void) {
@@ -25,6 +30,14 @@ void kbscan_event(void) {
     uint8_t layer = kbscan_layer;
     static uint8_t kbscan_last[KM_OUT] = { 0 };
 
+    // If timer 2 is finished
+    if (TF2) {
+        // Stop timer 2 running
+        TR2 = 0;
+        // Clear timer 2 finished flag
+        TF2 = 0;
+    }
+
     int i;
     for (i = 0; i < KM_OUT; i++) {
         // Set current line as output
@@ -47,6 +60,26 @@ void kbscan_event(void) {
                 bool new_b = new & (1 << j);
                 bool last_b = last & (1 << j);
                 if (new_b != last_b) {
+                    // If timer 2 is running
+                    if (TR2) {
+                        // Debounce releases
+                        if (!new_b) {
+                            // Restore bit, so that this release can be handled later
+                            new |= (1 << j);
+                            // Skip processing of release
+                            continue;
+                        }
+                    } else {
+                        // Begin debouncing on press
+                        if (new_b) {
+                            // Run timer 2 for 20 ms
+                            // 65536-(20000 * 69 + 89)/90 = 0xC419
+                            TH2 = 0xC4;
+                            TL2 = 0x19;
+                            TR2 = 1;
+                        }
+                    }
+
                     uint16_t key = keymap(i, j, kbscan_layer);
                     DEBUG("KB %d, %d, %d = 0x%04X, %d\n", i, j, kbscan_layer, key, new_b);
                     switch (key & KT_MASK) {