ref: 7ecfd641fb47e4a6ed475302bc1deac17473e704
dir: /home/serial.asm/
Serial:: push af push bc push de push hl ld a, [hSerialConnectionStatus] inc a jr z, .connectionNotYetEstablished ld a, [rSB] ld [hSerialReceiveData], a ld a, [hSerialSendData] ld [rSB], a ld a, [hSerialConnectionStatus] cp USING_INTERNAL_CLOCK jr z, .done ; using external clock ld a, START_TRANSFER_EXTERNAL_CLOCK ld [rSC], a jr .done .connectionNotYetEstablished ld a, [rSB] ld [hSerialReceiveData], a ld [hSerialConnectionStatus], a cp USING_INTERNAL_CLOCK jr z, .usingInternalClock ; using external clock xor a ld [rSB], a ld a, $3 ld [rDIV], a .waitLoop ld a, [rDIV] bit 7, a jr nz, .waitLoop ld a, START_TRANSFER_EXTERNAL_CLOCK ld [rSC], a jr .done .usingInternalClock xor a ld [rSB], a .done ld a, $1 ld [hSerialReceivedNewData], a ld a, SERIAL_NO_DATA_BYTE ld [hSerialSendData], a pop hl pop de pop bc pop af reti ; hl = send data ; de = receive data ; bc = length of data Serial_ExchangeBytes:: ld a, 1 ld [hSerialIgnoringInitialData], a .loop ld a, [hl] ld [hSerialSendData], a call Serial_ExchangeByte push bc ld b, a inc hl ld a, 48 .waitLoop dec a jr nz, .waitLoop ld a, [hSerialIgnoringInitialData] and a ld a, b pop bc jr z, .storeReceivedByte dec hl cp SERIAL_PREAMBLE_BYTE jr nz, .loop xor a ld [hSerialIgnoringInitialData], a jr .loop .storeReceivedByte ld [de], a inc de dec bc ld a, b or c jr nz, .loop ret Serial_ExchangeByte:: xor a ld [hSerialReceivedNewData], a ld a, [hSerialConnectionStatus] cp USING_INTERNAL_CLOCK jr nz, .loop ld a, START_TRANSFER_INTERNAL_CLOCK ld [rSC], a .loop ld a, [hSerialReceivedNewData] and a jr nz, .ok ld a, [hSerialConnectionStatus] cp USING_EXTERNAL_CLOCK jr nz, .doNotIncrementUnknownCounter call IsUnknownCounterZero jr z, .doNotIncrementUnknownCounter call WaitLoop_15Iterations push hl ld hl, wUnknownSerialCounter + 1 inc [hl] jr nz, .noCarry dec hl inc [hl] .noCarry pop hl call IsUnknownCounterZero jr nz, .loop jp SetUnknownCounterToFFFF .doNotIncrementUnknownCounter ld a, [rIE] and (1 << SERIAL) | (1 << TIMER) | (1 << LCD_STAT) | (1 << VBLANK) cp (1 << SERIAL) jr nz, .loop ld a, [wUnknownSerialCounter2] dec a ld [wUnknownSerialCounter2], a jr nz, .loop ld a, [wUnknownSerialCounter2 + 1] dec a ld [wUnknownSerialCounter2 + 1], a jr nz, .loop ld a, [hSerialConnectionStatus] cp USING_EXTERNAL_CLOCK jr z, .ok ld a, 255 .waitLoop dec a jr nz, .waitLoop .ok xor a ld [hSerialReceivedNewData], a ld a, [rIE] and (1 << SERIAL) | (1 << TIMER) | (1 << LCD_STAT) | (1 << VBLANK) sub (1 << SERIAL) jr nz, .skipReloadingUnknownCounter2 ld [wUnknownSerialCounter2], a ld a, $50 ld [wUnknownSerialCounter2 + 1], a .skipReloadingUnknownCounter2 ld a, [hSerialReceiveData] cp SERIAL_NO_DATA_BYTE ret nz call IsUnknownCounterZero jr z, .done push hl ld hl, wUnknownSerialCounter + 1 ld a, [hl] dec a ld [hld], a inc a jr nz, .noBorrow dec [hl] .noBorrow pop hl call IsUnknownCounterZero jr z, SetUnknownCounterToFFFF .done ld a, [rIE] and (1 << SERIAL) | (1 << TIMER) | (1 << LCD_STAT) | (1 << VBLANK) cp (1 << SERIAL) ld a, SERIAL_NO_DATA_BYTE ret z ld a, [hl] ld [hSerialSendData], a call DelayFrame jp Serial_ExchangeByte WaitLoop_15Iterations:: ld a, 15 .waitLoop dec a jr nz, .waitLoop ret IsUnknownCounterZero:: push hl ld hl, wUnknownSerialCounter ld a, [hli] or [hl] pop hl ret ; a is always 0 when this is called SetUnknownCounterToFFFF:: dec a ld [wUnknownSerialCounter], a ld [wUnknownSerialCounter + 1], a ret ; This is used to exchange the button press and selected menu item on the link menu. ; The data is sent thrice and read twice to increase reliability. Serial_ExchangeLinkMenuSelection:: ld hl, wLinkMenuSelectionSendBuffer ld de, wLinkMenuSelectionReceiveBuffer ld c, 2 ; number of bytes to save ld a, 1 ld [hSerialIgnoringInitialData], a .loop call DelayFrame ld a, [hl] ld [hSerialSendData], a call Serial_ExchangeByte ld b, a inc hl ld a, [hSerialIgnoringInitialData] and a ld a, 0 ld [hSerialIgnoringInitialData], a jr nz, .loop ld a, b ld [de], a inc de dec c jr nz, .loop ret Serial_PrintWaitingTextAndSyncAndExchangeNybble:: call SaveScreenTilesToBuffer1 callab PrintWaitingText call Serial_SyncAndExchangeNybble jp LoadScreenTilesFromBuffer1 Serial_SyncAndExchangeNybble:: ld a, $ff ld [wSerialExchangeNybbleReceiveData], a .loop1 call Serial_ExchangeNybble call DelayFrame call IsUnknownCounterZero jr z, .next1 push hl ld hl, wUnknownSerialCounter + 1 dec [hl] jr nz, .next2 dec hl dec [hl] jr nz, .next2 pop hl xor a jp SetUnknownCounterToFFFF .next2 pop hl .next1 ld a, [wSerialExchangeNybbleReceiveData] inc a jr z, .loop1 ld b, 10 .loop2 call DelayFrame call Serial_ExchangeNybble dec b jr nz, .loop2 ld b, 10 .loop3 call DelayFrame call Serial_SendZeroByte dec b jr nz, .loop3 ld a, [wSerialExchangeNybbleReceiveData] ld [wSerialSyncAndExchangeNybbleReceiveData], a ret Serial_ExchangeNybble:: call .doExchange ld a, [wSerialExchangeNybbleSendData] add $60 ld [hSerialSendData], a ld a, [hSerialConnectionStatus] cp USING_INTERNAL_CLOCK jr nz, .doExchange ld a, START_TRANSFER_INTERNAL_CLOCK ld [rSC], a .doExchange ld a, [hSerialReceiveData] ld [wSerialExchangeNybbleTempReceiveData], a and $f0 cp $60 ret nz xor a ld [hSerialReceiveData], a ld a, [wSerialExchangeNybbleTempReceiveData] and $f ld [wSerialExchangeNybbleReceiveData], a ret Serial_SendZeroByte:: xor a ld [hSerialSendData], a ld a, [hSerialConnectionStatus] cp USING_INTERNAL_CLOCK ret nz ld a, START_TRANSFER_INTERNAL_CLOCK ld [rSC], a ret Serial_TryEstablishingExternallyClockedConnection:: ld a, ESTABLISH_CONNECTION_WITH_EXTERNAL_CLOCK ld [rSB], a xor a ld [hSerialReceiveData], a ld a, START_TRANSFER_EXTERNAL_CLOCK ld [rSC], a ret