avr: added com2w2 (slightly improved version of com2w).

- move IRQ control to main code (only the main code knows exactly which
  combination of pins is used for com2)
- split one big module into multiple smaller files (easier to maintain)

avr/modules/com2w2/msgwrite.asm

@@ -0,0 +1,65 @@
+; ***************************************************************************
+; copyright   : (C) 2026 by Martin Preuss
+; email       : martin@libchipcard.de
+;
+; ***************************************************************************
+; * This file is part of the project "AqHome".                              *
+; * Please see toplevel file COPYING of that project for license details.   *
+; ***************************************************************************
+
+#ifndef AVR_MODULES_COM2W2_MSGWRITE_H
+#define AVR_MODULES_COM2W2_MSGWRITE_H
+
+
+.cseg
+
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w2SendMsg
+;
+; @param X pointer to bytes to send
+; @param Y pointer to interface data in SRAM
+; @return CFLAG set if message sent, cleared otherwise
+; @clobbers R16, R18 (R20, R22, R24, R25, X)
+
+com2w2SendMsg:
+  ldi r20, 6                           ; wait for about 60us for clock low
+  rcall com2w2WaitForClockLowMulti10Us  ; (R16, R20, R22)
+  brcs com2w2SendMsg_busy               ; CLK got low while waiting, so line is busy
+  push r15
+    in r15, SREG
+    cli                                 ; atomic disable irq and set CLK low
+    rcall com2w2DisableClkIrq            ; (none)
+    rcall com2w2ClkSetLow                ; reserve bus (none)
+    out SREG, r15
+  pop r15
+  adiw xh:xl, NETMSG_OFFS_MSGLEN
+  ld r18, X
+  sbiw xh:xl, NETMSG_OFFS_MSGLEN
+  inc r18                               ; adjust for DESTADDR
+  inc r18                               ; adjust for MSGLEN
+  inc r18                               ; adjust for CRCBYTE
+  rcall com2w2WaitTime1                  ; longer wait period (R22)
+  rcall com2w2SendBytes                  ; (r16, r17, r18, r22, X)
+  rcall com2w2ClkSetHigh                 ; make sure bus is released
+  rcall com2w2DataSetHigh
+
+  rcall com2w2EnableClkIrq               ; (none)
+  ldi r16, NET_IFACE_OFFS_PACKETSOUT_LOW
+  rcall NET_Interface_IncCounter16       ; (R24, R25)
+  sec
+  ret
+com2w2SendMsg_busy:
+  ldi r16, NET_IFACE_OFFS_ERR_BUSY_LOW
+  rcall NET_Interface_IncCounter16       ; (R24, R25)
+  clc
+  ret
+; @end
+
+
+
+
+#endif
+
+