From cb1285b0ab45336be5f0ade2bf2d6ebf9a3ae993 Mon Sep 17 00:00:00 2001
From: bruce33 <bruce33sw@gmail.com>
Date: Sun, 15 Jul 2018 11:10:55 +0100
Subject: [PATCH] core: improve timing in ps2_host_send to fix caps/num LEDs
 consistency

---
 tmk_core/protocol/ps2_busywait.c  | 7 ++++---
 tmk_core/protocol/ps2_interrupt.c | 7 ++++---
 tmk_core/protocol/ps2_usart.c     | 7 ++++---
 3 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/tmk_core/protocol/ps2_busywait.c b/tmk_core/protocol/ps2_busywait.c
index a64933219e..0fb9617a23 100644
--- a/tmk_core/protocol/ps2_busywait.c
+++ b/tmk_core/protocol/ps2_busywait.c
@@ -73,6 +73,9 @@ uint8_t ps2_host_send(uint8_t data)
     bool parity = true;
     ps2_error = PS2_ERR_NONE;
 
+    // see http://www.burtonsys.com/ps2_chapweske.htm but note that
+    // sending host->device samples on the rising not falling CLK edge
+
     /* terminate a transmission if we have */
     inhibit();
     wait_us(100); // 100us [4]p.13, [5]p.50
@@ -84,7 +87,6 @@ uint8_t ps2_host_send(uint8_t data)
 
     /* Data bit */
     for (uint8_t i = 0; i < 8; i++) {
-        wait_us(15);
         if (data&(1<<i)) {
             parity = !parity;
             data_hi();
@@ -92,17 +94,16 @@ uint8_t ps2_host_send(uint8_t data)
             data_lo();
         }
         WAIT(clock_hi, 50, 2);
+        // keyboard sampled the data, just before here, just as the clock goes high
         WAIT(clock_lo, 50, 3);
     }
 
     /* Parity bit */
-    wait_us(15);
     if (parity) { data_hi(); } else { data_lo(); }
     WAIT(clock_hi, 50, 4);
     WAIT(clock_lo, 50, 5);
 
     /* Stop bit */
-    wait_us(15);
     data_hi();
 
     /* Ack */
diff --git a/tmk_core/protocol/ps2_interrupt.c b/tmk_core/protocol/ps2_interrupt.c
index 0fd3d3600f..b1cd4d4686 100644
--- a/tmk_core/protocol/ps2_interrupt.c
+++ b/tmk_core/protocol/ps2_interrupt.c
@@ -72,6 +72,9 @@ uint8_t ps2_host_send(uint8_t data)
     bool parity = true;
     ps2_error = PS2_ERR_NONE;
 
+    // see http://www.burtonsys.com/ps2_chapweske.htm but note that
+    // sending host->device samples on the rising not falling CLK edge
+
     PS2_INT_OFF();
 
     /* terminate a transmission if we have */
@@ -85,7 +88,6 @@ uint8_t ps2_host_send(uint8_t data)
 
     /* Data bit[2-9] */
     for (uint8_t i = 0; i < 8; i++) {
-        _delay_us(15);
         if (data&(1<<i)) {
             parity = !parity;
             data_hi();
@@ -93,17 +95,16 @@ uint8_t ps2_host_send(uint8_t data)
             data_lo();
         }
         WAIT(clock_hi, 50, 2);
+        // keyboard sampled the data, just before here, just as the clock goes high
         WAIT(clock_lo, 50, 3);
     }
 
     /* Parity bit */
-    _delay_us(15);
     if (parity) { data_hi(); } else { data_lo(); }
     WAIT(clock_hi, 50, 4);
     WAIT(clock_lo, 50, 5);
 
     /* Stop bit */
-    _delay_us(15);
     data_hi();
 
     /* Ack */
diff --git a/tmk_core/protocol/ps2_usart.c b/tmk_core/protocol/ps2_usart.c
index 6936ca7b88..108b5cede7 100644
--- a/tmk_core/protocol/ps2_usart.c
+++ b/tmk_core/protocol/ps2_usart.c
@@ -78,6 +78,9 @@ uint8_t ps2_host_send(uint8_t data)
     bool parity = true;
     ps2_error = PS2_ERR_NONE;
 
+    // see http://www.burtonsys.com/ps2_chapweske.htm but note that
+    // sending host->device samples on the rising not falling CLK edge
+
     PS2_USART_OFF();
 
     /* terminate a transmission if we have */
@@ -91,7 +94,6 @@ uint8_t ps2_host_send(uint8_t data)
 
     /* Data bit[2-9] */
     for (uint8_t i = 0; i < 8; i++) {
-        _delay_us(15);
         if (data&(1<<i)) {
             parity = !parity;
             data_hi();
@@ -99,17 +101,16 @@ uint8_t ps2_host_send(uint8_t data)
             data_lo();
         }
         WAIT(clock_hi, 50, 2);
+        // keyboard sampled the data, just before here, just as the clock goes high
         WAIT(clock_lo, 50, 3);
     }
 
     /* Parity bit */
-    _delay_us(15);
     if (parity) { data_hi(); } else { data_lo(); }
     WAIT(clock_hi, 50, 4);
     WAIT(clock_lo, 50, 5);
 
     /* Stop bit */
-    _delay_us(15);
     data_hi();
 
     /* Ack */