From d73bedb51acd6c9b145e8b66c9e3207549599bf1 Mon Sep 17 00:00:00 2001
From: tmk <hasu@tmk-kbd.com>
Date: Sat, 16 Jan 2021 23:31:22 +0900
Subject: [PATCH] pc98_usb: Add RDY pulse in response receive #666

RDY high pulse(>=37us) is required to allow keyboard to send next data.
https://archive.org/stream/PC9800TechnicalDataBookHARDWARE1993/PC-9800TechnicalDataBook_HARDWARE1993#page/n157
---
 converter/pc98_usb/matrix.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/converter/pc98_usb/matrix.c b/converter/pc98_usb/matrix.c
index ce5a5b37..17335aa9 100644
--- a/converter/pc98_usb/matrix.c
+++ b/converter/pc98_usb/matrix.c
@@ -63,6 +63,13 @@ static int16_t pc98_wait_response(void)
     int16_t code = -1;
     uint8_t timeout = 255;
     while (timeout-- && (code = serial_recv2()) == -1) _delay_ms(1);
+
+    // Keyboards require RDY pulse >=37us to send next data
+    // https://archive.org/stream/PC9800TechnicalDataBookHARDWARE1993/PC-9800TechnicalDataBook_HARDWARE1993#page/n157
+    PC98_RDY_PORT |=  (1<<PC98_RDY_BIT);
+    _delay_us(40);
+    PC98_RDY_PORT &= ~(1<<PC98_RDY_BIT);
+
     xprintf("r%04X ", code);
     return code;
 }
@@ -176,11 +183,12 @@ uint8_t matrix_scan(void)
         }
     }
 
-    // PC-9801V keyboard requires RDY pulse.
-    // This is not optimal place though, it works.
-    PC98_RDY_PORT |=  (1<<PC98_RDY_BIT);    // RDY: high
-    _delay_us(20);
-    PC98_RDY_PORT &= ~(1<<PC98_RDY_BIT);    // RDY: low
+    // Keyboards require RDY pulse >=37us to send next data
+    // https://archive.org/stream/PC9800TechnicalDataBookHARDWARE1993/PC-9800TechnicalDataBook_HARDWARE1993#page/n157
+    PC98_RDY_PORT |=  (1<<PC98_RDY_BIT);
+    _delay_us(40);
+    PC98_RDY_PORT &= ~(1<<PC98_RDY_BIT);
+
     return code;
 }
 
-- 
2.48.1