avr/modules/flash: make protocol more robust

- wait for ATTN high after error receiving a packet
- use different wait times when waiting for FLASH_START and FLASH_DATA

avr/modules/flash/flashprocess.asm

@@ -48,6 +48,7 @@ checkFlash:
   rcall ioRawSendMsg                   ; (r16, r17, X)
 
   ldi r16, NETMSG_CMD_FLASH_START
+  ldi r20, FLASH_WAITFORSTART_TRIES
   rcall ioWaitForGivenMsg              ; (r16, r17, r18, r19, r20, r22, X)
   brcc checkFlash_end
   
@@ -59,8 +60,8 @@ checkFlash:
   ldi xl, LOW(flashRecvBuffer)
   ldi xh, HIGH(flashRecvBuffer)
   rcall flashProcessHandleFlashStart
-  brcc checkFlash_end
-  sec
+;  brcc checkFlash_end
+;  sec
 checkFlash_end:
   ret
 ; @end
@@ -80,6 +81,7 @@ flashProcess:
 flashProcess_loop1:
     ; wait up to 10s for incoming FLASH_DATA message
     ldi r16, NETMSG_CMD_FLASH_DATA
+    ldi r20, FLASH_WAITFORDATA_TRIES
     rcall ioWaitForGivenMsg            ; (r16, r17, r18, r19, r20, r22, X)
     brcc flashProcess_end              ; no FLASH_DATA or FLASH_END msg
     ; either FLASH_DATA or FLASH_END received
@@ -186,7 +188,7 @@ flashProcessHandleFlashData_sendResponse:
   pop r16
 #endif
 
-  ldi r24, 50
+  ldi r24, 25
   rcall flashWaitForMillisecs                ; (R22, R24)
   rcall flashProcessSendFlashResponse        ; (R16, R17, R18, R19, R20, X)
   sbi LED_PIN, LED_PINNUM                    ; toggle