; ***************************************************************************
; copyright   : (C) 2023 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.   *
; ***************************************************************************



; ***************************************************************************
; defines

.equ COM_MAXWAIT_US               = 100  ; maximum wait time in microseconds when waiting for rising/falling clock

.equ COM_MAINTENANCE_ADDR         = 0xf1

.equ COM_BUFFER_FLAGS_DONE        = 0x80
.equ COM_BUFFER_FLAGS_RECEIVED    = 0x40
.equ COM_BUFFER_FLAGS_TOSEND      = 0x20
.equ COM_BUFFER_FLAGS_RELEASED    = 0x10
.equ COM_BUFFER_FLAGS_PRIO1       = 0x08
.equ COM_BUFFER_FLAGS_PRIO0       = 0x04
.equ COM_BUFFER_FLAGS_IFACE1      = 0x02
.equ COM_BUFFER_FLAGS_IFACE0      = 0x01

.equ COM_BUFFER_PRIO_INFO         = 0
.equ COM_BUFFER_PRIO_NORMAL       = COM_BUFFER_FLAGS_PRIO0
.equ COM_BUFFER_PRIO_IMPORTANT    = COM_BUFFER_FLAGS_PRIO1
.equ COM_BUFFER_PRIO_VITAL        = (COM_BUFFER_FLAGS_PRIO0 | COM_BUFFER_FLAGS_PRIO1)

.equ COM_REPEAT_INFO              = 3
.equ COM_REPEAT_NORMAL            = 32
.equ COM_REPEAT_IMPORTANT         = 64
.equ COM_REPEAT_VITAL             = 255

.equ COM_BUFFER_NUM               = 6
.equ COM_BUFFER_SIZE              = 24 ; CAVE: Need to change routine COM_BufferPosToY when changing this value!!


.equ COM_BUFFER_OFFS_FLAGS        = 0 ; first byte in buffer is flags byte
.equ COM_BUFFER_OFFS_DATA         = 1

.equ COM_MSG_OFFS_DESTADDR        = 0
.equ COM_MSG_OFFS_MSGLEN          = 1
.equ COM_MSG_OFFS_MSGDATA         = 2
.equ COM_MSG_OFFS_CMD             = 2 ; first at COM_MSG_OFFS_MSGDATA
.equ COM_MSG_OFFS_SRCADDR         = 3
.equ COM_MSG_OFFS_PAYLOAD         = 4 ; payload for the cmd follows here

.equ COM_ERR_NOTFORME             = 1
.equ COM_ERR_CHECKSUM             = 2
.equ COM_ERR_IO                   = 3


; ***************************************************************************
; data

.dseg


comDataBegin:
  comFlags:               .byte 1
  comAddress:             .byte 1
  comRepeatCount:         .byte 1
  comReserved1:           .byte 1

  comInterrupts:          .byte 2

  comStatsPacketsIn:      .byte 2
  comStatsPacketsOut:     .byte 2

  comStatsRecvErrs:       .byte 2
  comStatsRecvCrcErrs:    .byte 2
  comStatsMissed:         .byte 2
  comStatsIgnored:        .byte 2
  comStatsHandled:        .byte 2

  comStatsCollisions:     .byte 2
  comStatsAborted:        .byte 2
  
  comStatsSendNoBuffer:   .byte 2
  comStatsRecvNoBuffer:   .byte 2

  comRecvBuffersReadPos:  .byte 1
  comRecvBuffersWritePos: .byte 1
  comRecvBuffersUsed:     .byte 1
  comMaxBuffersUsed:      .byte 1
  comRecvBuffers:         .byte (COM_BUFFER_SIZE*COM_BUFFER_NUM)
comDataEnd:



; ***************************************************************************
; code

.cseg

COM_BEGIN:


comIsrPcint0:
  push r15
    in r15, SREG
    sbic COM_PIN_ATTN, COM_PINNUM_ATTN
      rjmp comIsrPcint0_end
    ; low, read packet
    push r1
      push r16
        push r17
          push r18
            push r19
              push r20
                push r21
                  push r22
                    push xh
                     push xl
                       push yh
                         push yl
                           lds xl, comInterrupts
                           lds xh, comInterrupts+1
                           adiw xh:xl, 1
                           sts comInterrupts, xl
                           sts comInterrupts+1, xh
                           rcall comReceivePacketHandleBuffer ; (R1, R16, R17, R18, R19, R20, R21, R22, X, Y
                         pop yl
                       pop yh
                     pop xl
                    pop xh
                  pop r22
                pop r21
              pop r20
            pop r19
          pop r18
        pop r17
      pop r16
    pop r1
    
comIsrPcint0_end:
  pop r15
  reti



; ---------------------------------------------------------------------------
; Com_Init
;
; IN:
; OUT:
; - CFLAG: set if okay, clear on error
; USED: R16, R17, X, Y

Com_Init:
  ; preset SRAM data area
  ldi xh, HIGH(comDataBegin)
  ldi xl, LOW(comDataBegin)
  clr r16
  ldi r17, (comDataEnd-comDataBegin)
  rcall Utils_FillSram

  ; set address to 0 (will be updated later)
  clr r16
  sts comAddress, r16

  ; setup pins and interrupts
  cbi COM_PORT_DATA, COM_PINNUM_DATA      ; disable internal pullup for DATA
  cbi COM_DDR_DATA, COM_PINNUM_DATA       ; set DATA port as input

  cbi COM_PORT_ATTN, COM_PINNUM_ATTN      ; disable internal pullup for ATTN
  cbi COM_DDR_ATTN, COM_PINNUM_ATTN       ; set ATTN port as input

  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
  
  ldi r16, (1<<COM_IRQ_GIFR_ATTN)         ; clear pending irq by writing 1 to ATTN bit
  out GIFR, r16
  
  sec
  ret



; ---------------------------------------------------------------------------
; Com_Run
;
; IN:
; - nothing
; OUT:
; - CFLAG: set if something done, can be called again immediately (otherwise: wait for timer interrupt and retry)
; REGS: (R1, R3, R16, R17, R18, R19, R22, X)

Com_Run:
  rcall comHandleNextPacketInQueue ; nothing more than handling packages in ringbuffer
;  clc
  ret



; ---------------------------------------------------------------------------
; Mark a packet as enqueued.
;
; IN:
; - Y: pointer to buffer containing the enqueued packet
; - R20: priority
; OUT:
; - CFLAG: set if okay, clear otherwise
; MODIFIED REGS: R15, R16

COM_EnqueuePacket:
  in r15, SREG
  cli
    ldd r16, y+COM_BUFFER_OFFS_FLAGS
    andi r16, (~(COM_BUFFER_FLAGS_PRIO1 | COM_BUFFER_FLAGS_PRIO0 | COM_BUFFER_FLAGS_RECEIVED | COM_BUFFER_FLAGS_DONE)) & 0xff
    or r16, r20                       ; add priority
    ori r16, COM_BUFFER_FLAGS_TOSEND
    std y+COM_BUFFER_OFFS_FLAGS, r16
  out SREG, r15                       ; restore IRQ flag
  sec
  ret



; ---------------------------------------------------------------------------
; comHandleNextPacketInQueue
;
; IN:
; - nothing
; OUT:
; - CFLAG: set if something done, can be called again immediately (otherwise: wait for timer interrupt and retry)
; MODIFIED REGS: R16, R17, Y (R15, R18, R21, R22, X)


comHandleNextPacketInQueue:
  lds r16, comRecvBuffersUsed
  tst r16
  breq comHandleNextPacketInQueue_retNc          ; no buffers in use
  
  lds r16, comRecvBuffersReadPos
  rcall COM_BufferPosToY                         ; get current read buffer to Y (R16, R17)
  ldd r16, y+COM_BUFFER_OFFS_FLAGS               ; get flags
  ; check for released buffer (dealloc)
  mov r17, r16
  andi r17, COM_BUFFER_FLAGS_RELEASED            ; check for buffer released
  brne comHandleNextPacketInQueue_releaseBuffer
  ; check for received packet
  mov r17, r16
  andi r17, COM_BUFFER_FLAGS_RECEIVED
  brne comHandleNextPacketInQueue_receivedPacket
  ; check for buffer to send
  mov r17, r16
  andi r17, COM_BUFFER_FLAGS_TOSEND              ; check for message to send
  brne comHandleNextPacketInQueue_sendPacket
  ; nothing to do (e.g. buffer not ready to be sent)
  rjmp comHandleNextPacketInQueue_retNc
comHandleNextPacketInQueue_sendPacket:
  rcall comSendPacketHandleRepeat                ; (R15, R16, R17, R18, R21, R22, X)
  ret                                            ; use CFLAG from subroutine
comHandleNextPacketInQueue_receivedPacket:
  clr r17
  sts comRepeatCount, r17                        ; set comRepeatCount to zero
  rcall comHandleReceivedPacket                  ; (r16, r17, r21, X)
  sec                                            ; always return with set CFLAG
  ret
comHandleNextPacketInQueue_releaseBuffer:
  rcall COM_BufferDeallocFront
  sec                                            ; always return with set CFLAG
  ret
comHandleNextPacketInQueue_retNc:
  clc
  ret



; ---------------------------------------------------------------------------
; comHandleReceivedPacket
;
; IN:
; - Y: pointer to current buffer (pointed to by comRecvBuffersReadPos)
; OUT:
; - nothing
; MODIFIED REGS: X (r16, r17, r21)


comHandleReceivedPacket:
  rcall onPacketReceived 
  brcs comHandleReceivedPacket_l1
  ldi xl, LOW(comStatsIgnored)
  ldi xh, HIGH(comStatsIgnored)
  rjmp comHandleReceivedPacket_l2
comHandleReceivedPacket_l1:
  ldi xl, LOW(comStatsHandled)
  ldi xh, HIGH(comStatsHandled)
comHandleReceivedPacket_l2:
  rcall comDeallocReadBufAndIncrCounter ; (r16, r17, r21)
  ret




.include "com_lowlevel.asm"
.include "com_buffer.asm"
.include "com_crc.asm"
.include "com_send.asm"
.include "com_recv.asm"



COM_END:
.equ MODULE_SIZE_COM = COM_END-COM_BEGIN