158 lines
5.4 KiB
NASM
158 lines
5.4 KiB
NASM
; ***************************************************************************
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; copyright : (C) 2024 by Martin Preuss
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; email : martin@libchipcard.de
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;
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; ***************************************************************************
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; * This file is part of the project "AqHome". *
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; * Please see toplevel file COPYING of that project for license details. *
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; ***************************************************************************
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; ---------------------------------------------------------------------------
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; @routine uartBitbang_ReceivePacketIntoBuffer
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;
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; Receive a packet into buffer pointed to by X.
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; Expects interrupts to be disabled.
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;
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; @param R16 COM address to listen to
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; @param R17 maximum value for accepted msg data (i.e. buffersize minus 3)
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; @param X buffer to receive to
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; @return CFLAG set if okay (packet received), cleared on error
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; @return R16 error code if CFLAG is cleared (COM2_ERROR_NOTFORME, COM2_ERROR_IOERROR, COM2_ERROR_DATAERROR)
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; @clobbers: r16, r17, r18, X (r19, r20, r21, r22)
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uartBitbang_ReceivePacketIntoBuffer:
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mov r18, r17
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push r16
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; read destination address
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rcall uartBitbang_ReceiveByte ; read byte (R16, R17, R20, R21, R22)
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pop r17 ; pop from R16 to R17
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brcc uartBitbang_ReceivePacketIntoBuffer_ioError
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#ifndef COM_ACCEPT_ALL_DEST ; accept every destination address
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; compare destination address (accept "FF" and own address)
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cp r16, r17
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breq uartBitbang_ReceivePacketIntoBuffer_acceptAddr
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cpi r16, 0xff
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breq uartBitbang_ReceivePacketIntoBuffer_acceptAddr
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ldi r16, COM2_ERROR_NOTFORME
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rjmp uartBitbang_ReceivePacketIntoBuffer_error ; clc/ret
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#endif
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uartBitbang_ReceivePacketIntoBuffer_acceptAddr:
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st X+, r16 ; store dest address, lock buffer
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; read msg length
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rcall uartBitbang_ReceiveByte ; read packet length (R16, R17, R20, R21, R22)
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brcc uartBitbang_ReceivePacketIntoBuffer_ioError
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st X+, r16
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cp r16, r18 ; (COM2_BUFFER_SIZE-3)
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brcc uartBitbang_ReceivePacketIntoBuffer_contentError ; packet too long
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inc r16 ; account for checksum byte
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mov r17, r16
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uartBitbang_ReceivePacketIntoBuffer_loop:
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push r17
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rcall uartBitbang_ReceiveByte ; read byte (R16, R17, R20, R21, R22)
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pop r17
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brcc uartBitbang_ReceivePacketIntoBuffer_ioError
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st X+, r16
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dec r17
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brne uartBitbang_ReceivePacketIntoBuffer_loop
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sec
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ret
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uartBitbang_ReceivePacketIntoBuffer_ioError:
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ldi r16, COM2_ERROR_IOERROR
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rjmp uartBitbang_ReceivePacketIntoBuffer_error
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uartBitbang_ReceivePacketIntoBuffer_contentError:
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ldi r16, COM2_ERROR_DATAERROR
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uartBitbang_ReceivePacketIntoBuffer_error:
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clc
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ret
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; @end
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; ---------------------------------------------------------------------------
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; @routine uartBitbang_SendPacket
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;
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; Send packet over wire, handle ATTN line.
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;
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; @param X ptr to buffer to send
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; @return CFLAGS set if okay, cleared otherwise (errorcode in R16)
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; @clobbers R16, R22 (R17, R21, X)
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uartBitbang_SendPacket:
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rcall uartBitbang_AcquireBus
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brcc uartBitbang_SendPacket_lineBusyError
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rcall uartBitbang_WaitForOneBitLength ; wait for one bit duration (R22)
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rcall uartBitbang_WaitForOneBitLength ; wait for one bit duration (R22)
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adiw xh:xl, COM2_MSG_OFFS_MSGLEN
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ld r17, X
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sbiw xh:xl, COM2_MSG_OFFS_MSGLEN
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inc r17 ; account for dest addr
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inc r17 ; account for msglen byte
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inc r17 ; account for crc byte
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uartBitbang_SendPacket_loop:
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ld r16, X+
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rcall uartBitbang_SendByte ; send byte (R16, R21, R22)
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brcc uartBitbang_SendPacket_releaseBusRet
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dec r17
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brne uartBitbang_SendPacket_loop
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sec
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uartBitbang_SendPacket_releaseBusRet:
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cbi COM_ATTN_DDR, COM_ATTN_PIN ; release ATTN line (by setting direction to IN)
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brcc uartBitbang_SendPacket_ioError
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; packet successfully sent
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ret
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uartBitbang_SendPacket_ioError:
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ldi r16,COM2_ERROR_COLLISION
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ret
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uartBitbang_SendPacket_lineBusyError:
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ldi r16,COM2_ERROR_BUSY
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ret
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; @end
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; ---------------------------------------------------------------------------
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; @routine uartBitbang_AcquireBus
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;
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; Reserve bus if free (otherwise return error)
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; Expects interrupts to be disabled.
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;
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; @return CFLAG set if okay (bus acquired), cleared on error
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; @clobbers: none
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uartBitbang_AcquireBus:
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; check for ATTN line: busy?
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cbi COM_ATTN_DDR, COM_ATTN_PIN ; set ATTN as input
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cbi COM_ATTN_OUTPUT, COM_ATTN_PIN ; disable pullup on ATTN
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nop ; needed to sample current input
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sbis COM_ATTN_INPUT, COM_ATTN_PIN ; ATTN low?
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rjmp uartBitbang_AcquireBus_busy ; jump if it is
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sbi COM_ATTN_DDR, COM_ATTN_PIN ; set ATTN as output
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cbi COM_ATTN_OUTPUT, COM_ATTN_PIN ; set ATTN low
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sec
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ret
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uartBitbang_AcquireBus_busy:
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clc
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ret
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; @end
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; ---------------------------------------------------------------------------
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; @routine uartBitbang_WaitForOneBitLength
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;
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; wait for one bit length (minus cycles for call and ret).
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;
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; @clobbers r22
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uartBitbang_WaitForOneBitLength:
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Utils_WaitNanoSecs COM_BIT_LENGTH, 7, r22 ; wait for one bit duration (minus RCALL/RET)
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ret
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; @end
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