From 6468e76545e572d69784049950684a12353c7790 Mon Sep 17 00:00:00 2001
From: Martin Preuss <martin@aquamaniac.de>
Date: Wed, 18 Jan 2023 01:09:31 +0100
Subject: [PATCH] Added and simplified COM module.

Directly use pins, no complicated redirections.
Router modules will probably use real UARTs or MCUs programmed as UARTs.
---
 avr/com.asm   | 508 ++++++++++++++++++++++++++++++++------------------
 avr/main.asm  |  58 +++---
 avr/utils.asm |  45 +++++
 3 files changed, 402 insertions(+), 209 deletions(-)

diff --git a/avr/com.asm b/avr/com.asm
index 3cb2d0e..a1263c4 100644
--- a/avr/com.asm
+++ b/avr/com.asm
@@ -1,121 +1,34 @@
 
 
 
-.equ COM_BIT_LENGTH = 52000 ; 104000=9600, 52000=19200, 26000=38400
+; ***************************************************************************
+; defines
 
+.equ COM_MAXWAIT                   = 200  ; maximum loop count when waiting for rising/falling clock (TODO: Make frequency-dependant)
 
-.equ COM_DATA_OFFS_ID              = 0
-.equ COM_DATA_OFFS_FLAGS           = 1
-.equ COM_DATA_OFFS_ADDR_DDR_DATA   = 2
-.equ COM_DATA_OFFS_ADDR_PORT_DATA  = 3
-.equ COM_DATA_OFFS_ADDR_PIN_DATA   = 4
-.equ COM_DATA_OFFS_PINMASK_DATA    = 5
-.equ COM_DATA_OFFS_ADDR_DDR_ATTN   = 6
-.equ COM_DATA_OFFS_ADDR_PORT_ATTN  = 7
-.equ COM_DATA_OFFS_ADDR_PIN_ATTN   = 8
-.equ COM_DATA_OFFS_PINMASK_ATTN    = 9
-.equ COM_DATA_OFFS_IRQNUM_ATTN     = 10 ; 0 for PCINT0, 1 for PCINT1
-.equ COM_DATA_OFFS_IRQMASK_ATTN    = 11 ; e.g. 0x80 for PCINT7 in PCMSK0
-.equ COM_DATA_SIZE                 = 12
 
 .equ COM_BUFFER_FLAGS_DONE        = 0x80
 .equ COM_BUFFER_FLAGS_RECEIVED    = 0x40
 
 
-; interface data in SRAM
-.equ COM_SRAM_OFFS_ID                = 0
-.equ COM_SRAM_OFFS_FLAGS             = 1
-.equ COM_SRAM_OFFS_ADDRESS           = 2
-.equ COM_SRAM_OFFS_MODULE_ID         = 3
-.equ COM_SRAM_OFFS_SUBNET_START      = 4
-.equ COM_SRAM_OFFS_SUBNET_END        = 5
-
-.equ COM_SRAM_OFFS_DATA_BITMASK      = 6
-.equ COM_SRAM_OFFS_DATA_INPUT_PORT   = 7
-.equ COM_SRAM_OFFS_DATA_OUTPUT_PORT  = 8
-.equ COM_SRAM_OFFS_DATA_DDR_PORT     = 9
-
-.equ COM_SRAM_OFFS_ATTN_BITMASK      = 10
-.equ COM_SRAM_OFFS_ATTN_INPUT_PORT   = 11
-.equ COM_SRAM_OFFS_ATTN_OUTPUT_PORT  = 12
-.equ COM_SRAM_OFFS_ATTN_DDR_PORT     = 13
-
-.equ COM_SRAM_OFFS_STAT_PACKETS_IN   = 14 ; 2 bytes
-.equ COM_SRAM_OFFS_STAT_PACKETS_OUT  = 16 ; 2 bytes
-.equ COM_SRAM_OFFS_STAT_COLLISIONS   = 18 ; 2 bytes
-.equ COM_SRAM_OFFS_STAT_RECVERR      = 20 ; 2 bytes
-.equ COM_SRAM_OFFS_STAT_MISSED       = 22 ; 2 bytes
-
-.equ COM_SRAM_SIZE                   = 24
-
-
 
 
 ; ***************************************************************************
-; macros
-
-
-
-; ---------------------------------------------------------------------------
-; comSetRamBitInX
-;
-; Set a given bit in the byte pointed to by X.
-; IN:
-; - @0: bit mask to check
-; - @1: temporary register to use
-; OUT:
-; - nothing
-; MODIFIED REGS: temporary register
-; CYCLES: 4
-
-.macro comSetRamBitInX
-  ld @1, x              ; 1
-  or @1, @0             ; 1
-  st x, @1              ; 2
-.endmacro
-
-
-
-; ---------------------------------------------------------------------------
-; comClearRamBitInX
-;
-; Clear a given bit in the byte pointed to by X.
-; IN:
-; - @0: bit mask to check
-; - @1: temporary register to use
-; OUT:
-; - nothing
-; MODIFIED REGS: temporary register
-; CYCLES: 6 (CAVE: two cycles more than comSetRamBitInX!)
-
-.macro comClearRamBitInX
-  ld @1, x              ; 1
-  com @0                ; 1
-  and @1, @0            ; 1
-  com @0                ; 1
-  st x, @1              ; 2
-.endmacro
-
-
-
-; ---------------------------------------------------------------------------
-; comTestRamBitInX
-;
-; Test a given bit in the byte pointed to by X.
-; IN:
-; - @0: bit mask to check
-; - @1: temporary register to use
-; OUT:
-; - ZFLAG: set if bit is zero, cleared otherwise
-; MODIFIED REGS: temporary register
-; CYCLES: 6 (CAVE: two cycles more than comSetRamBitInX!)
-
-.macro comTestRamBitInX
-  ld @1, x              ; 1
-  and @1, @0            ; 1
-.endmacro
+; data
+
+.dseg
 
 
+comDataBegin:
+  comFlags:           .byte 1
+  comAddress:         .byte 1
+  comStatsPacketsIn:  .byte 2
+  comStatsPacketsOut: .byte 2
+  comStatsRecvErrs:   .byte 2
+  comStatsCollisions: .byte 2
+  comStatsMissed:     .byte 2
+  comRingBuffer:      .byte RINGBUFFER_OFFS_DATA+COM_RINGBUFFER_SIZE
+comDataEnd:
 
 
 
@@ -130,105 +43,332 @@
 ; Com_Init
 ;
 ; IN:
-; - Y: pointer to SRAM data
-; - Z: pointer to FLASH data
 ; OUT:
 ; - CFLAG: set if okay, clear on error
 ; USED: 
 
 Com_Init:
-  mov xh, yh
-  mov xl, yl
+  ; preset SRAM data area
+  ldi xh, HIGH(comDataBegin)
+  ldi xl, LOW(comDataBegin)
   clr r16
-  ldi r17, COM_SRAM_SIZE
+  ldi r17, (comDataEnd-comDataBegin)
   rcall Utils_FillSram
 
-  ; copy data from flash to sram
-  push zh
-    push zl
-      lsl zl
-      rol zh
-    
-      lpm r16, z+ ; id
-      std y+COM_SRAM_OFFS_ID, r16
-      lpm r16, z+ ; flags
-      std y+COM_SRAM_OFFS_FLAGS, r16
-      lpm r16, z+ ; ADDR_DDR_DATA
-      std y+COM_SRAM_OFFS_DATA_DDR_PORT, r16
-      lpm r16, z+ ; ADDR_PORT_DATA
-      std y+COM_SRAM_OFFS_DATA_OUTPUT_PORT, r16
-      lpm r16, z+ ; ADDR_PIN_DATA
-      std y+COM_SRAM_OFFS_DATA_INPUT_PORT, r16
-      lpm r16, z+ ; PINMASK_DATA
-      std y+COM_SRAM_OFFS_DATA_INPUT_PORT, r16
-      lpm r16, z+ ; ADDR_DDR_ATTN
-      std y+COM_SRAM_OFFS_ATTN_DDR_PORT, r16
-      lpm r16, z+ ; ADDR_PORT_ATTN
-      std y+COM_SRAM_OFFS_ATTN_OUTPUT_PORT, r16
-      lpm r16, z+ ; ADDR_PIN_ATTN
-      std y+COM_SRAM_OFFS_ATTN_INPUT_PORT, r16
-      lpm r16, z+ ; PINMASK_ATTN
-      std y+COM_SRAM_OFFS_ATTN_INPUT_PORT, r16
-      lpm r17, z+ ; IRQNUM_ATTN
-      lpm r18, z+ ; COM_DATA_OFFS_IRQMASK_ATTN
-    pop zl
-  pop zh
+  ; init ringbuffer
+  ldi r16, COM_RINGBUFFER_SIZE
+  ldi yl, LOW(comRingBuffer)
+  ldi yh, HIGH(comRingBuffer)
+  rcall RingBuffer_Init
 
-  ; set DATA port as input
-  clr xh
-  ldd xl, y+COM_SRAM_OFFS_DATA_DDR_PORT
-  ldd r4, y+COM_SRAM_OFFS_DATA_BITMASK
-  comClearRamBitInX r4, r16
-  ; disable internal pullup for DATA
-  ldd xl, y+COM_SRAM_OFFS_DATA_OUTPUT_PORT
-  comClearRamBitInX r4, r16
+  ; setup pins and interrupts
+  sbi COM_DDR_DATA, COM_PINNUM_DATA       ; set DATA port as input
+  cbi COM_PORT_DATA, COM_PINNUM_DATA      ; disable internal pullup for DATA
 
-  ; set ATTN as input
-  ldd xl, y+COM_SRAM_OFFS_ATTN_DDR_PORT
-  ldd r4, y+COM_SRAM_OFFS_ATTN_BITMASK
-  comClearRamBitInX r4, r16
-  ; disable internal pullup for DATA
-  ldd xl, y+COM_SRAM_OFFS_ATTN_OUTPUT_PORT
-  comClearRamBitInX r4, r16
+  sbi COM_DDR_ATTN, COM_PINNUM_ATTN       ; set ATTN port as input
+  cbi COM_PORT_ATTN, COM_PINNUM_ATTN      ; disable internal pullup for ATTN
+
+  sbi COM_IRQ_ADDR_ATTN, COM_IRQ_BIT_ATTN ; enable pin change irq for ATTN line
+  in r16, GIMSK                           ; enable pin change irq PCIE0 or PCIE1
+  ori r16, (1<<COM_IRQ_GIMSK_ATTN)
+  out GIMSK, R16
+  in r16, GIFR                            ; clear pending irq
+  andi r16, ~(1<<COM_IRQ_GIFR_ATTN)
+  out GIFR, r16
   
-  ; setup pin IRQ for ATTN (intnum in r17, irqmask in r18)
-  tst r17
-  brne Com_Init_setupInt1
-Com_Init_setupInt0:
-  ; enable PCIE0
-  in r16, GIMSK
-  ori r16, (1 << PCIE0)
-  out GIMSK, r16
-  ; clear pending interrupts
-  in r16, GIFR
-  andi r16, ~(1 << PCIF0)
-  out GIFR, r16
-  ldi xl, PCMSK0+0x20
-  rjmp Com_Init_enablePinIrq
-Com_Init_setupInt1:
-  ; enable PCIE1
-  in r16, GIMSK
-  ori r16, (1 << PCIE1)
-  out GIMSK, r16
-  ; clear pending interrupts
-  in r16, GIFR
-  andi r16, ~(1 << PCIF1)
-  out GIFR, r16
-  ldi xl, PCMSK1+0x20
-Com_Init_enablePinIrq:
-  ld r16, x
-  or r16, r18         ; set mask bits
-  st x, r16
   sec
   ret
 
 
 
+; ---------------------------------------------------------------------------
+; comSendPacket
+;
+; Send a packet.       (TODO: input buffer in x, length in r16)
+;
+; IN:
+; - R18: pos pointer inside ring buffer to read from next
+; OUT:
+; - CFLAG: set if okay, clear otherwise
+; MODIFIED REGS: R10, R11, R12, R16, R20 (R3, R21, R22)
+
+comSendPacket:
+  ldi yl, LOW(comRingBuffer)
+  ldi yh, HIGH(comRingBuffer)
+  ldd r19, y+RINGBUFFER_OFFS_MAXSIZE
+  rcall RingBuffer_Read          ; read entry length from buffer (advances r18) (R3, R22)
+  cpi r16, 3                     ; at least 3 bytes?
+  brcs comSendPacket_error       ; too few bytes
+  mov r10, r16                   ; r10: number of bytes at current ringbuffer pos
+  dec r10
+  dec r10
+  dec r10                        ; r10: number of bytes in message
+  clr r11                        ; r11: XOR checksum
+  mov r20, r18                   ; store pos of flags in buffer for later ref
+  rcall RingBuffer_Read          ; read flags from buffer
+  mov r12, r16                   ; r12: flags
+  rcall RingBuffer_Read          ; read dest address from buffer
+  eor r11, r16                   ; calculate checksum
+  rcall comSendByte              ; send destination address (R16, R21, R22)
+  brcc comSendPacket_error
+  mov r16, r10                   ; send msg length
+  eor r11, r16                   ; calculate checksum
+  rcall comSendByte              ; send destination address
+  brcc comSendPacket_error
+  tst r10                        ; payload?
+  breq comSendPacket_sendCrc     ; no payload, go send checksum
+comSendPacket_loop:
+    rcall RingBuffer_Read        ; read byte from buffer
+    eor r11, r16                 ; calculate checksum
+    rcall comSendByte            ; send byte
+    brcc comSendPacket_error
+    dec r10
+  brne comSendPacket_loop
+comSendPacket_sendCrc:
+  mov r16, r10                   ; send checksum
+  rcall comSendByte              ; send byte
+  brcc comSendPacket_error
+  mov r18, r20                   ; pos of flags byte in ringbuffer
+  mov r16, r12
+  ori r16, COM_BUFFER_FLAGS_DONE ; set flag
+  rcall RingBuffer_Write         ; write new flags (R3, R22)
+  sec
+  ret
+
+comSendPacket_error:
+  clc
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; comReceivePacket
+;
+; Receive a packet. If we are the recipient of the packet then space will be allocated inside the
+; given ringbuffer and the received packet will be stored there.
+;
+; Packages are stored in the buffer like this:
+; - 1 byte : buffer size
+; - 1 byte: flags (e.g. WAN_BUFFER_RECEIVED)
+; - 1 byte : destination address
+; - n bytes: packet (i.e. buffer size -2 bytes)
+;
+; IN:
+; - nothing
+; OUT:
+; - CFLAG: set if okay, clear otherwise
+; MODIFIED REGS: R1, R2, R3, R16, R17, R18, R19 (R20, R21, R22, XL, XH)
+
+comReceivePacket:
+  ldi yl, LOW(comRingBuffer)
+  ldi yh, HIGH(comRingBuffer)
+  clr r1                                       ; r1: checksum
+  ; read destination address
+  rcall comReceiveByte                         ; read byte
+  brcc comReceivePacket_error
+  ; compare destination address (accept "0" and own address)
+  tst r16
+  breq comReceivePacket_acceptAddr
+  lds r17, comAddress
+  cp r16, r17
+  breq comReceivePacket_acceptAddr
+  clc                                          ; not for me
+  ret
+comReceivePacket_acceptAddr:
+  mov r3, r16                                  ; r3: destination address (maybe we need to forward the packet)
+  eor r1, r16
+  rcall comReceiveByte                         ; read packet length (R16, R17, R20, R21, R22)
+  brcc comReceivePacket_error
+  ; alloc ring buffer
+  mov r17, r16                                 ; r17: packet length
+  inc r16                                      ; packet length bytes + length byte
+  inc r16                                      ; + flags
+  inc r16                                      ; + dest addr
+  mov r2, r16                                  ; r2: number of bytes allocated in ringbuffer
+  push r17
+    rcall RingBuffer_Alloc                     ; (r16, r17, r18, r19, r20, r21)
+  pop r17
+  brcc comReceivePacket_error
+  mov r18, r16                                 ; r18: pos in ring buffer
+  ldd r19, y+RINGBUFFER_OFFS_MAXSIZE           ; max size
+  mov r16, r2                                  ; write number of bytes allocated to ringbuffer
+  ori r16, COM_BUFFER_FLAGS_RECEIVED
+  rcall RingBuffer_Write                       ; (r3, r22)
+  ldi r16, COM_BUFFER_FLAGS_RECEIVED           ; write flags to ringbuffer
+  rcall RingBuffer_Write                       ; (r3, r22)
+  mov r16, r3                                  ; write destination address for packet we saved earlier
+  rcall RingBuffer_Write                       ; (r3, r22)
+  ; read packet (except XOR byte, that will be read later)
+comReceivePacket_loop1:
+    rcall comReceiveByte                       ; (R16, R17, R20, R21, R22)
+    brcc comReceivePacket_error_release_buffer
+    eor r1, r16
+    rcall RingBuffer_Write                     ; (r3, r22)
+    dec r17
+  brne comReceivePacket_loop1
+  ; read XOR byte, don't store
+  rcall comReceiveByte                         ; (R16, R17, R20, R21, R22)
+  brcc comReceivePacket_error
+  eor r1, r16
+  brne comReceivePacket_error_release_buffer   ; XOR should be 0 here, otherwise error
+  sec
+  ret
+comReceivePacket_error_release_buffer:
+  mov r16, r2                                  ; number of bytes allocated in ringbuffer
+  rcall RingBuffer_DeallocWrite                ; (r17, r18, r19, r20, r21)
+comReceivePacket_error:
+  clc
+  ret
+
+
+
+
+; ---------------------------------------------------------------------------
+; comSendByte
+;
+; Send a byte.
+; We only set the data pin to low at the beginning for the startbit. After that
+; we only change the pin direction (e.g. input vs output):
+; - for 0 bit: set DDR to output, forcing the data line low
+; - for 1 bit: set DDR to input, letting the external pullup R pull the data line to HIGH
+;              since the output pin is still set to 0 the internal pullup is disabled
+; IN:
+; - R16: byte to send
+; OUT:
+; - CFLAG: set if okay, clear otherwise
+; MODIFIED REGS: R16, R21, R22
+
+comSendByte:
+  ldi r21, 8                                   ; +1 bits left
+  ; send startbit
+  cbi COM_PORT_DATA, COM_PINNUM_DATA           ; +2 set DATA low
+  sbi COM_DDR_DATA, COM_PINNUM_DATA            ; +2 set DATA as output
+  Utils_WaitNanoSecs COM_BIT_LENGTH, 5, r22    ; wait for on bit duration
+  ; send remaining bits
+comSendByte_loop:
+    lsr r16                                    ; 1+ bit to send -> CARRY
+    brcc comSendByte_setHigh                   ; HI: +2, LO: +1
+comSendByte_setLow:
+    sbi COM_DDR_DATA, COM_PINNUM_DATA          ; +2 set DATA as output
+    nop
+    rjmp comSendByte_waitBit                   ; +2
+comSendByte_setHigh:
+    cbi COM_DDR_DATA, COM_PINNUM_DATA          ; +2 set DATA as input, pullup R makes it ONE
+    nop                                        ; +1 (to make pin change available)
+    sbic COM_PIN_DATA, (1<<COM_PINNUM_DATA)    ; +1 if okay, +2 otherwise
+      rjmp comSendByte_error                   ; +2 if error
+comSendByte_waitBit:                           ; 7 cycles in this loop until now
+    Utils_WaitNanoSecs COM_BIT_LENGTH, 10, r22
+    dec r21                                    ; +1
+  brne comSendByte_loop                        ; +2, sum per loop: 10 cycles
+  ; send stopbit
+  cbi COM_DDR_DATA, COM_PINNUM_DATA            ; +2 set DATA as input, pullup R makes it ONE
+  Utils_WaitNanoSecs COM_BIT_LENGTH, 4, r22
+  sec
+  ret
+
+comSendByte_error:
+  clc
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; comReceiveByte
+;
+; Receive a byte.
+;
+; IN:
+; - nothing
+; OUT:
+; - CFLAG: set if okay, clear otherwise
+; - R16: byte read (if CFLAG set)
+; MODIFIED REGS: R16, R20, R21, R22 (R17)
+
+comReceiveByte:
+  sbi COM_DDR_DATA, COM_PINNUM_DATA            ; set DATA port as input
+  cbi COM_PORT_DATA, COM_PINNUM_DATA           ; disable internal pullup for DATA
+  ldi r21, 8                                   ; bits left
+  clr r20                                      ; byte currently receiving
+  ; wait for startbit
+  rcall comWaitForDataLow
+  brcc comReceiveByte_error
+  Utils_WaitNanoSecs COM_BIT_LENGTH/2, 5, r22  ; goto middle of startbit to maximize sync stability
+comReceiveByte_loop:
+    Utils_WaitNanoSecs COM_BIT_LENGTH, 8, r22  ; 8 cycles used in the complete loop between waits
+    sec                                        ; +1
+    sbic COM_PIN_DATA, COM_PINNUM_DATA         ; LOW: +2, HIGH: +1
+      rjmp comReceiveByte_shiftIn              ; HIGH: +2, rjmp, use set CFLAG
+    clc                                        ; LOW: +1
+comReceiveByte_shiftIn:
+    ror r20                                    ; +1
+    dec r21                                    ; +1
+  brne comReceiveByte_loop                     ; +2, sum per loop: 8 cycles
+  rcall comWaitForDataHigh                     ; wait for start of stopbit
+;  brcc comReceiveByte_error
+  mov r16, r20
+  sec
+  ret
+comReceiveByte_error:
+  clc
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; comWaitForDataLow
+;
+; Waits up to COM_MAXWAIT loops for low data line
+; IN:
+; OUT:
+; - CFLAG: set if okay, clear otherwise
+; MODIFIED REGISTERS: r17, r22, X
+
+comWaitForDataLow:
+  ldi r17, COM_MAXWAIT
+
+comWaitForDataLow_loop:
+    sbis COM_PIN_DATA, COM_PINNUM_DATA
+      rjmp comWaitForDataLow_done
+    dec r17
+  brne comWaitForDataLow_loop
+  clc   ; timeout
+  ret
+
+comWaitForDataLow_done:
+  sec   ; ok
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; comWaitForDataHigh
+;
+; Waits up to COM_MAXWAIT loops for high data line
+; IN:
+; OUT:
+; - CFLAG: set if okay, clear otherwise
+; MODIFIED REGISTERS: r17, r22, X
+
+comWaitForDataHigh:
+  ldi r17, COM_MAXWAIT
+
+comWaitForDataHigh_loop:
+    sbic COM_PIN_DATA, COM_PINNUM_DATA
+      rjmp comWaitForDataHigh_done
+    dec r17
+  brne comWaitForDataHigh_loop
+  clc   ; timeout
+  ret
+
+comWaitForDataHigh_done:
+  sec   ; ok
+  ret
+
+
+
 
 
 
 
 
-
-
-
diff --git a/avr/main.asm b/avr/main.asm
index 91323b9..b1b9677 100644
--- a/avr/main.asm
+++ b/avr/main.asm
@@ -7,24 +7,35 @@
 ; ***************************************************************************
 ; defines
 
+; ---------------------------------------------------------------------------
+; generic
+
+.equ clock=1000000 ; Define the clock frequency
+
+
+
 ; ---------------------------------------------------------------------------
 ; COM module
 
-.equ COM_DDR_DATA DDRA
-.equ COM_PORT_DATA PORTA
-.equ COM_PIN_DATA PINA
-.equ COM_PINMASK_DATA (1<<PORTA1)
-.equ COM_PINNUM_DATA PORTA1
+.equ COM_BIT_LENGTH      = 52000 ; 104000=9600, 52000=19200, 26000=38400
 
-.equ COM_DDR_ATTN DDRA
-.equ COM_PORT_ATTN PORTA
-.equ COM_PIN_ATTN PINA
-.equ COM_PINMASK_ATTN (1<<PORTA7)
-.equ COM_PINNUM_ATTN PORTA7
+.equ COM_RINGBUFFER_SIZE = 32    ; 32 bytes for now
+
+.equ COM_DDR_DATA        = DDRA
+.equ COM_PORT_DATA       = PORTA
+.equ COM_PIN_DATA        = PINA
+.equ COM_PINNUM_DATA     = PORTA1
+
+.equ COM_DDR_ATTN        = DDRA
+.equ COM_PORT_ATTN       = PORTA
+.equ COM_PIN_ATTN        = PINA
+.equ COM_PINNUM_ATTN     = PORTA7
+
+.equ COM_IRQ_ADDR_ATTN   = PCMSK0
+.equ COM_IRQ_BIT_ATTN    = 7              ; bit 7 in PCMSK0
+.equ COM_IRQ_GIFR_ATTN   = PCIF0
+.equ COM_IRQ_GIMSK_ATTN  = PCIE0
 
-.equ COM_IRQ_ADDR_ATTN PCMSK0
-.equ COM_IRQ_MASK_ATTN (1<<7)  ; bit 7 in PCMSK0
-.equ COM_IRQ_GIFR_ATTN (1 << PCIF0)
 
 
 
@@ -34,7 +45,9 @@
 .cseg
 .org 000000
 
-; ***************************************************************************
+
+
+; ---------------------------------------------------------------------------
 ; Reset and interrupt vectors
 
 	rjmp main ; Reset vector
@@ -60,11 +73,11 @@
 ; ***************************************************************************
 ; includes
 
+.include "utils.asm"
 .include "ringbuffer.asm"
 .include "timer.asm"
 .include "led.asm"
 .include "com.asm"
-.include "utils.asm"
 
 
 
@@ -74,7 +87,6 @@
 .dseg
 
 ledA3Sram:   .byte LED_SRAM_SIZE
-wanA7A1Sram: .byte COM_SRAM_SIZE
 
 
 
@@ -83,11 +95,7 @@ wanA7A1Sram: .byte COM_SRAM_SIZE
 
 .cseg
 
-ledA3Flash:   .db DDRA+0x20, PORTA+0x20, PINA+0x20, (1<<PORTA3)
-comA7A1Flash: .db 1, 0                                          ; id, flags
-              .db DDRA+0x20, PORTA+0x20, PINA+0x20, (1<<PORTA1) ; port info for DATA line
-              .db DDRA+0x20, PORTA+0x20, PINA+0x20, (1<<PORTA7) ; port info for ATTN line
-              .db 0, 0x80                                       ; ATTN: PCINT irq type, irq mask (e.g. for PCMSK0)
+ledA3Flash:    .db DDRA+0x20, PORTA+0x20, PINA+0x20, (1<<PORTA3)
 blinkPattern:  .db 5, 5, 5, 5, 5, 10, 0xff, 0xff   ; 3 short blinks, 1s pause, restart
 
 
@@ -134,7 +142,7 @@ main_loop:
 
 
 
-; ***************************************************************************
+; ---------------------------------------------------------------------------
 ; initModules
 ;
 ; Call init functions of the used modules. Add your routine calls here.
@@ -157,7 +165,7 @@ initModules:
 
 
 
-; ***************************************************************************
+; ---------------------------------------------------------------------------
 ; runModulesUntilIdle
 ;
 ; Call run functions of the used modules. Add your routine calls here.
@@ -178,7 +186,7 @@ runModulesUntilIdle_Timer:       ; repeat this block for every run function
 
 
 
-; ***************************************************************************
+; ---------------------------------------------------------------------------
 ; onEvery100ms
 ;
 ; Called every 100ms. Add your routine calls here.
@@ -203,7 +211,7 @@ onEvery100ms:
 
 
 
-; ***************************************************************************
+; ---------------------------------------------------------------------------
 ; onEverySecond
 ;
 ; Called every second. Add your routine calls here.
diff --git a/avr/utils.asm b/avr/utils.asm
index 34a1448..24c4ea1 100644
--- a/avr/utils.asm
+++ b/avr/utils.asm
@@ -1,6 +1,47 @@
 
 
 
+; Utils_WaitNanoSecs  waittime_in_ns , cyles_already_used , waitcount_register 
+;
+;     cycles already used will be subtracted from the delay
+;     the waittime resolution is 1 cycle (delay from exact to +1 cycle)
+;     the maximum delay at 20MHz (50ns/clock) is 38350ns
+;     waitcount register must specify an immediate register
+; taken from https://www.mikrocontroller.net/articles/AVR_Assembler_Makros#Verz%C3%B6gerung_um_X_Nanosekunden
+;
+.set     Osc_Hz         = clock                    ; 1 MHz
+.set     cycle_time_ns  = (1000000000 / Osc_Hz)      ; clock duration
+.macro   Utils_WaitNanoSecs
+  .set cycles = ((@0 + cycle_time_ns - 1) / cycle_time_ns - @1)
+  .if (cycles > (255 * 3 + 2))
+    .error "MACRO Utils_WaitNanoSecs - too many cycles to burn"
+  .else
+    .if (cycles > 6)
+      .set  loop_cycles = (cycles / 3)      
+      ldi   @2,loop_cycles
+      dec   @2
+      brne  pc-1
+      .set  cycles = (cycles - (loop_cycles * 3))
+    .endif
+    .if (cycles > 0)
+      .if   (cycles & 4)
+        rjmp  pc+1
+        rjmp  pc+1
+      .endif
+      .if   (cycles & 2)
+        rjmp  pc+1
+      .endif
+      .if   (cycles & 1)
+        nop
+      .endif
+    .endif
+  .endif
+.endmacro
+
+
+
+
+
 ; ***************************************************************************
 ; Utils_FillSram
 ;
@@ -49,3 +90,7 @@ Utils_IncrementCounter32:
   st -x, r18
   ret
 
+
+
+
+