128 lines
7.2 KiB
C
128 lines
7.2 KiB
C
/*
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####################################################################################
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# #
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# Bildschirmtricks Firmware V2.0.0 #
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# dbt03 emulator layer #
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# #
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# Copyright (C) 2008 Philipp Fabian Benedikt Maier (aka. Dexter) #
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# #
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# This program is free software; you can redistribute it and/or modify #
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# it under the terms of the GNU General Public License as published by #
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# the Free Software Foundation; either version 2 of the License, or #
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# (at your option) any later version. #
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# #
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# This program is distributed in the hope that it will be useful, #
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# but WITHOUT ANY WARRANTY; without even the implied warranty of #
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the #
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# GNU General Public License for more details. #
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# #
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# You should have received a copy of the GNU General Public License #
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# along with this program; if not, write to the Free Software #
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# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA #
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# #
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#################################################################################### */
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/* ## HEADER ########################################################################## */
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#ifndef DBT03_H
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#define DBT03_H
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/*
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==OVERVIEW==
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Note: Every BTX Terminal was connected to a propritary modem that that could only dial the number
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of the BTX-Mainframe (PAD). The microcontroller in the modem also conained a secret that was
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necessary to associate with the BTX-Mainfraime. The Modem were sealed and opening was a
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punishable offence.
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2 7=START (Power modem up and initaiate connection)
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o 5=ED (Data receive and status report, 1200 baud, 8n1)
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4 o o 5 6=SD (Data send port, 75 baud)
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1 o o 3 2=E (GND)
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6 o o 7
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^
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View at the
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terminal/modem
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side
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The DBT03 was a V.23 modem from the BUNDESPOST (a telecommunications service in germany, now history)
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to dial into the BTX (=BILDSCHIRMTEXT) system. This modem was switched on by pulling the the START
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line to high. Then the modem dials automaticly and does the BTX negotiation. Then the modem reports
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the connection status in a very easy way: It just takes the dialtones and hands them through as normal
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TTL signals.
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________________________________________________________________________________________
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START ___|
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___ Start bits ____
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| Stop bit ___ |
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V | V
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_______________ ______________ ______ _ _ _ _ _ _ V _
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ED ___| |||||||| ||||||| ||||||_____| |_| |_| |_| |_|.|____ And so on....
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<---------------><-----><------------><-----><----><----><----><---Serial data at 1200 Baud-->
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T1 T2 T3 T4 T5 T6 T7
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(dialtone) (dialing) (ring)
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T1: Time between modem activision and hook-off, typicaly 3s.
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Configurable with DBT03_HOOK_OFF_DELAY macro.
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T2: Dialtone appeareance time, a dialtone cycle is about 2,35ms long.
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Number of cyceles is configurable with DBT03_DAILTONE_CYCLES
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T3: Dialin delay time, time that goes by whil a real modem dials the BTX-PAD number (019 or 01910)
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Typicaly it takes 4 seconds to dial that number. The dialin delay time is configurable
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with DBT03_DIALIN_DELAY
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T4: Ringtone appearance time, nealy the same as T2 but in this case this tone stands for
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a successful dial process and tells the BTX-Terminal that the pone of the BTX-PAD is ringing.
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In this emulation we assume that the BTX-PAD is fast and hooks off with the first ringtone.
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The ringtone-appeareance-time is configurable with DBT03_RINGTONE_CYCLES
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T5: Post ringtone delay, time between the dialtone and the carrier signal. This time can be configured
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with DBT03_POST_RINGTONE_DELAY
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T6: Carrier tone appereance time: The original DBT-03 modem needed about 1,6 - 1,7 ms time to detect the
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carrier signal. As long as the carrier signal is not recognized the modem passes the signal through.
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That is why the carrier signal is also a part of this simulation.
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T7: To finish the dialin procedure the modem pulls the ED line to low level and waits some time.
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This time is configurable with DBT03_POST_DIALIN_DELAY
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Note: The configured values are based on some old documentation i found on the net as well as on
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experiments with various types of terminals. if this does not work on your setup or if you
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unhappy with the long dialin procedure you can try to tune the timing.
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==CONFIGURATION== */
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/* Timing configuration for serial data transmission */
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#define DBT03_TX_BAUDRATE 82 /* (x10us) Should be 1200 baud/833,333us bit legth */
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#define DBT03_RX_BAUDRATE 133 /* (x100us) Should be 75 baud/13,333ms bit legth */
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/* Timing configuration for dialin simulation */
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#define DBT03_HOOK_OFF_DELAY 30 /* (x100ms) Hook off delay time, typical 3,0s */
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#define DBT03_DAILTONE_CYCLES 800 /* (x2,35ms) Dialtone appearance time */
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#define DBT03_DIALIN_DELAY 40 /* (x100ms) Dailin delay time, maximum 4,3s */
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#define DBT03_RINGTONE_CYCLES 200 /* (x2,35ms) Ringtone appearance time */
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#define DBT03_POST_RINGTONE_DELAY 5 /* (x100ms) Time between ringtone and carrier tone */
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#define DBT03_CARRIERTONE_CYCLES 2080 /* (x760us) Carrier tone appereance time */
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#define DBT03_POST_DIALIN_DELAY 5 /* (x100ms) Time between successful dialin notification and transmission start */
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/* ==Function set==
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This proviedes a set of basic functions that emulate the typical dbt03 signals */
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void systemDbt03Init(void); /* Initalize dbt03 emulation layer */
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void systemDbt03Transmit(uint8_t character); /* Send character to the BTX-Terminal */
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uint8_t systemDbt03Receive(void); /* Receive a character from the BTX-Terminal */
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void systemDbt03ConnectionOk(void); /* Tell the BTX-Terminal that connection went ok */
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void systemDbt03ConnectionTerminate(void); /* Tell the BTX-Terminal that the connection has terminated */
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#endif /*DBT03_H*/
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/* #################################################################################### */
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