From cc7ef0cf3037d43fa7f6d963d2294b3419271c2f Mon Sep 17 00:00:00 2001
From: Martin Preuss <martin@aquamaniac.de>
Date: Wed, 7 May 2025 20:03:58 +0200
Subject: [PATCH] flash: wait for ATTN high before waiting for message.

this helps with syncing.
---
 avr/modules/flash/io_bitbang.asm | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/avr/modules/flash/io_bitbang.asm b/avr/modules/flash/io_bitbang.asm
index 48b42e7..16999a0 100644
--- a/avr/modules/flash/io_bitbang.asm
+++ b/avr/modules/flash/io_bitbang.asm
@@ -101,14 +101,14 @@ ioRawInit:
 ioRawSendMsg:
 ioRawSendMsg_loop:
     ldi r16, 0xff                        ; expect ATTN high
-    ldi r17, 3
-    rcall ioWaitForAttnState100ms     ; wait for up to 300ms
+    ldi r17, 10
+    rcall ioWaitForAttnState100ms        ; wait for up to 1s
     brcs ioRawSendMsg_attnHigh
     ret
 ioRawSendMsg_attnHigh:
     ldi xl, LOW(flashSendBuffer)
     ldi xh, HIGH(flashSendBuffer)
-    rcall ioRawSendPacket             ; R16, R22 (R17, R21, X)
+    rcall ioRawSendPacket                ; R16, R22 (R17, R21, X)
   brcc ioRawSendMsg_loop
   ret
 ; @end
@@ -117,12 +117,21 @@ ioRawSendMsg_attnHigh:
 
 ; ---------------------------------------------------------------------------
 ; @routine ioRawWaitForValidMsg
+;
 ; Wait for valid incoming msg
 ;
+; First waits for ATTN line to go high (released) then wait for ATTN
+; line to go low. This way we will only start listening at the beginning of
+; a message.
+;
 ; @return CFLAG set if okay (packet received), cleared on error
 ; @clobbers: r16, r17 (r18, r19, r20, r21, r22, X)
 
 ioRawWaitForValidMsg:
+  ldi r16, 0xff                         ; expect ATTN high
+  ldi r17, 100
+  rcall ioWaitForAttnState100ms         ; wait for up to 10s
+  brcc ioRawWaitForValidMsg_end         ; ATTN not high, exit
   ldi r16, 0                            ; expect ATTN low
   ldi r17, 100
   rcall ioWaitForAttnState100ms         ; wait for up to 10s
@@ -322,7 +331,7 @@ ioRawAcquireBus:
   cbi COM_ATTN_OUTPUT, COM_ATTN_PIN              ; disable pullup on ATTN
   nop                                            ; needed to sample current input
   sbis COM_ATTN_INPUT, COM_ATTN_PIN              ; ATTN low?
-    rjmp ioRawAcquireBus_busy             ; jump if it is
+    rjmp ioRawAcquireBus_busy                    ; jump if it is
   sbi COM_ATTN_DDR, COM_ATTN_PIN                 ; set ATTN as output
   cbi COM_ATTN_OUTPUT, COM_ATTN_PIN              ; set ATTN low
   sec