From 87788fa93cfb30a0a30b91bc8004eae772b4a2a7 Mon Sep 17 00:00:00 2001
From: Martin Preuss <martin@aquamaniac.de>
Date: Sat, 23 Aug 2025 00:09:39 +0200
Subject: [PATCH] avr: wait for free CLK line on error when in flash mode

---
 avr/modules/flash/io_com2w.asm | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/avr/modules/flash/io_com2w.asm b/avr/modules/flash/io_com2w.asm
index 08c835f..cfc9fe1 100644
--- a/avr/modules/flash/io_com2w.asm
+++ b/avr/modules/flash/io_com2w.asm
@@ -270,7 +270,7 @@ com2wRecvMsg_loop:
   rjmp com2wRecvMsg_end
 com2wRecvMsg_eBadSize:
 com2wRecvMsg_eIo:
-com2wRecvMsg_clcRet:
+  rcall com2wRecvByteWaitForQuietClk      ; (r18, r20, r22)
   clc
 com2wRecvMsg_end:
   ret
@@ -278,6 +278,32 @@ com2wRecvMsg_end:
 
 
 
+; ---------------------------------------------------------------------------
+; @routine com2wRecvByteWaitForQuietClk
+;
+; Wait until the clock line is consistently high for 1ms.
+;
+; @clobbers r18, r20, r22
+
+com2wRecvByteWaitForQuietClk:
+  ldi r18, 200
+com2wRecvByteWaitForQuietClk_loop:
+      ldi r20, 100                          ; wait up to 1ms for clock high (R20, R22)
+      rcall com2wWaitForClockLowMulti10Us
+      brcs com2wRecvByteWaitForQuietClk_waitForLow
+      dec r18
+    brne com2wRecvByteWaitForQuietClk_loop
+    rjmp com2wRecvByteWaitForQuietClk_ret
+com2wRecvByteWaitForQuietClk_waitForLow:
+    ldi r20, 100                          ; wait up to 1ms for clock low (R20, R22)
+    rcall com2wWaitForClockLowMulti10Us
+    brcc com2wRecvByteWaitForQuietClk_ret ; not low within 1ms, assume line is quiet
+  brne com2wRecvByteWaitForQuietClk_loop
+com2wRecvByteWaitForQuietClk_ret:
+  ret
+
+
+
 ; ---------------------------------------------------------------------------
 ; @routine com2wRecvByte
 ;