From 4270a2dfa5d6ce2947d1d1832e1e1e2a5591e239 Mon Sep 17 00:00:00 2001
From: Tobias Diedrich <ranma+git@tdiedrich.de>
Date: Sat, 22 Jan 2022 23:50:42 +0100
Subject: [PATCH] Check for slave clock stretching

This indeed fixes the values read back:
80000000ff  No buttons, no movement
80010000ff  Left button
80050000ff  Left+right buttons
80070000ff  All buttons
800012fdff  Force applied
80000fffff  force applied
---
 main.s | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/main.s b/main.s
index 9436f1c..d350272 100644
--- a/main.s
+++ b/main.s
@@ -1512,7 +1512,9 @@ _i2c_sda0:
 
 _i2c_scl1:
 	B0BCLR tpSCLM  ; Set SCL to input
-	JMP $+1
+@@:
+	B0BTS1 tpSCL   ; Wait until SCL high
+	JMP @B
 	NOP
 	RET
 
@@ -1524,7 +1526,7 @@ _i2c_scl0:
 
 _i2c_start:
 	CALL _i2c_sda1   ; 8 cycles
-	CALL _i2c_scl1   ; 8 cycles
+	CALL _i2c_scl1   ; 8+N cycles
 	CALL _i2c_sda0   ; 8 cycles
 	CALL _i2c_scl0   ; 8 cycles
 	RET