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Chapter 6: Modem Stuff 86 6 Modem Stuff Modems are finicky beasts, and cajoling them into talking to your Fnordadel properly can be a tricky piece of business. This chapter, then, deals with the various modem configuration options in Fnordadel, and gives some tips on how to make a recalcitrant modem behave. 6.1 Basic Modem Requirements To run a Fnordadel, you must have a modem possessing a modicum of basic features. These are: o Must be able to auto-answer the phone. o Must be able to respond to DTR (Data Terminal Ready) line control by the computer. DTR is supposed to be pin 20 on the RS-232 connector. Ideally, the modem should be able to hang up the phone, disable auto answer, and go to `command' mode when the computer flips DTR off (and reverse the above when DTR goes high). o Must have the CD (Carrier Detect) line tracking the status of the carrier. CD (or DCD) is supposed to be pin 8 on the RS-232 connector. o If you want to do any calling out (i.e., during networking or whatever), the modem must be able to autodial the phone using a command string. Most modems are perfectly capable of all of the above. If your modem is advertised as being ``Hayes-compatible'', then it *should* work fine. The DTR and CD settings will likely have to be adjusted, since most modems do not by default listen to DTR and most leave the CD line high all the time. These behaviours can be changed either by using a DIP-switch or in the software; it's almost always possible. STadel 3.3b, from which Fnordadel is descended, was advertised to work with the following list of modems, and there's no reason to believe that we've introduced any incompatibilities: o Avatex 1200, 1200E, 1200HC, 2400HC o Everex 2400 o FastComm 19200 o Hayes 1200, 2400 o Incomm 2400 o MultiTech 1200, 2400 o Prometheus 2400B2 o Supra 2400 Chapter 6: Modem Stuff 87 o Telebit Trailblazer 19,200 o USR Courier 2400, HST 9600 The Fnordadel developers both use the Supra 2400; we've been running 24 hours a day for a few years now and have had no problems with the wee beasties. Your mileage may vary, of course. 6.2 Setting Up the Modem If your modem meets the above criteria, then we're off. (If it doesn't, then go buy a real modem---1200 and 2400 baud Hayes compatible modems are dirt cheap these days.) In this section we'll describe some of the `ctdlcnfg.sys' options for the modem. 6.2.1 Baud rate You must tell Fnordadel the highest baud rate at which the modem will function; this is accomplished by setting the variable #sysbaud in `ctdlcnfg.sys'. #sysbaud can have any one of the following values: 0 300 bps only 1 300 and 1200 bps 2 300, 1200 and 2400 bps 3 300, 1200, 2400 and 9600 bps 4 300 up to 19200 bps Note that 4800 bps is not supported. The ST serial port will do 4800, but we've never heard of a modem that will, other than ones that will also go faster. If for some reason you find yourself in dire need of 4800, see Appendix A [Fnordadel Support], page 170. 6.2.2 Initialisation Hayes compatible modems, at least, understand a set of commands to control their behaviour. Fnordadel requires that the modem be set up in a certain way; thus, you must define a command string which will be sent to the modem every time Fnordadel wants to reset the modem. Simply put a line like the following: #modemsetup "AT &C1 &D2 V0 E0 M0 Q0 X4 S0=1\r%10" in your `ctdlcnfg.sys'. The example above will work on many Hayes-compatible modems. The various parts mean: o The initial `AT' tells the modem that a command string is coming. Chapter 6: Modem Stuff 88 o `&C1 &D2' sets up the required behaviour for the CD and DTR lines (see Section 6.1 [Basic Modem Requirements], page 86). If your modem controls CD and DTR with hardware switches, it probably will not support these commands, so you may have to remove them. o `V0 E0 M0 Q0' selects numeric result codes (see Section 6.2.3.2 [Result codes], page 89), turns off command echoing, turns off the built-in speaker, and turns on result codes. o `X4' tells the modem to return the full range of result codes (see Section 6.2.3.2 [Result codes], page 89). o `S0=1' tells the modem to answer the phone on the first ring. o `\r' represents a carriage return, which must be there to terminate the command string. o And finally, `%10' is a special notation which causes Fnordadel to pause for 10 tenths of a second (i.e., one second). This is necessary for some modems, which take a comparatively long time to process the command string. (See the front of `ctdlcnfg.doc' for more on the format of these sorts of string variables.) Please be warned that your modem may not recognise some or all of the above codes; they may be different, or absent, or whatever. We've seen some pretty mental modem behaviour, so be sure to read your modem manual. A trick which has proved useful with many modems is as follows: If the modem allows you to save its settings in non-volatile RAM (i.e., if the settings can be preserved when the modem is powered off), then you can use a terminal program of some kind to manually set up the modem the way Fnordadel wants it, by sending your version of the above command string to the modem. Then use the command to save settings (usually `AT&W' or something). At this point you can simply use `ATZ\r%10' as the #modemsetup string; `ATZ' has the effect of resetting the modem to the saved state. The advantage of this is that the string is shorter, so it can speed things up a bit, especially during networking or auto-dialing when the modem is being reset many times. 6.2.3 Baud-rate detection Fnordadel must be able to detect the baud rate of incoming calls, and it has a couple of ways to accomplish this. The first is by searchbaud, and the second is using result codes. Result codes are by far the better method, and since most modems can support the feature, we recommend it. Chapter 6: Modem Stuff 89 6.2.3.1 Searchbaud If you define the `ctdlcnfg.sys' variable #searchbaud to be `1', it will cause Fnordadel to loop through the range of supported baud rates (as defined by #sysbaud; see Section 6.2.1 [Baud rate], page 87), waiting one-half second at each rate for a carriage return (`<CR>') from the caller. The upshot of this is that callers must hit `<CR>' once or twice when they connect with the BBS. If #searchbaud is `0', then your BBS will work at *only* the highest baud rate represented by #sysbaud. This is last-resort stuff, kids. You should normally run with #searchbaud set to `1' unless your modem absolutely fails to properly detect other speed connections. (If your modem is this stupid, it might be time to consider getting another one.) The variable #connectprompt modifies the behaviour of #searchbaud slightly; if defined to be `1', it causes Fnordadel to loop through the baud rates, spitting out a prompt which says ``Type return'' and waiting for a `<CR>' for a while; it does all this until the user hits `<CR>' at some baud rate, or until it gives up. Anyway, this is all pretty ugly, really; a far better method is to use result codes. 6.2.3.2 Result codes Most modems, Hayes-compatible ones included, will send a code to the computer when they pick up a carrier; furthermore, they can usually be configured to return a different code depending on the speed of the connection. We utilise this to our advantage. There is a `ctdlcnfg.sys' variable for each baud rate that Fnordadel supports (#reply300 through #reply19200) which you should set to match the string that your modem returns when it connects at that baud rate. For example: #reply300 "1" #reply1200 "5" #reply2400 "10" are the usual settings for a Hayes-compatible 2400-baud modem. (As always, your mileage may vary.) Please note that the defined reply strings must be sent (by the modem) terminated with a carriage return; however, don't put `\r' in the #reply strings. (i.e., if the 300 baud reply sent from the modem is `1\r', use `#reply300 "1"'.) If you've got the #reply strings defined in `ctdlcnfg.sys', then Fnordadel will use the result code method instead of the searchbaud stuff. You must have a #reply string for each permissible baud rate (i.e., if you defined `sysbaud 1', then you need a #reply300 and a #reply1200 defined before Fnordadel will use the result code method.) Chapter 6: Modem Stuff 90 Note also that you must have the modem set up to return the codes properly. See Section 6.2.2 [Initialisation], page 87. 6.2.3.3 2400-baud operation Many 2400-baud modems have a slight quirk. They will not connect with a 2400 baud caller unless they have been initialised with the serial port set at 2400 baud; they will, however, connect with any lower baud rate no matter what speed they're initialised at. We don't know why this is; but if your modem is like this, there's a `ctdlcnfg.sys' parameter (well, two, actually) which will help. Simply define the variable #init-speed to be the baud rate at which the modem should be initialised; the permissible values are the same as for #sysbaud (see Section 6.2.1 [Baud rate], page 87). In the case of the quirky 2400 baud modems, put `init-speed 2' and the problem will go away. Another way of fixing it is to define #hs-bug to be `1'. This causes Fnordadel to initialise the modem at the highest supported baud rate, which is specified by #sysbaud. Either method works. 6.2.3.4 Connect delay Some modems, we understand, will croak if a character is sent to them too quickly after they connect with an incoming caller. This could happen if you've got both searchbaud and connectprompt set. If it does happen, then set connectdelay to be the number of seconds to wait after carrier is first detected, before sending anything. 6.2.4 Dialing out If you want to do any networking, or if you just want to use your Fnordadel as a terminal program, then you have to tell it some stuff about how to make your modem dial the phone. 6.2.4.1 The dialing commands The relevant `ctdlcnfg.sys' variables are #calloutprefix and #calloutsuffix. As you'd expect, they should be defined as the strings used to start and end a dialing command. The string sent to the modem will consist of: <calloutprefix><number><calloutsuffix> For Hayes-compatible modems, the following settings work: #calloutprefix "ATD" #calloutsuffix "\r" An optional `T' or `P' may be put after `ATD' to specify Touch-Tone or Pulse (rotary) dialing. If your modem is not standard Hayes, then look it up in the manual. Chapter 6: Modem Stuff 91 6.2.4.2 Long-distance dialing If the variable #usa is defined to be `1', then Fnordadel assumes it is in North America and will form the dial string for a long-distance number as follows: <calloutprefix>1<area code><number><calloutsuffix> If #usa is `0', Fnordadel will simply spit the number out as-is. 6.2.4.3 Timing Two more `ctdlcnfg.sys' variables are used to tell Fnordadel how long to wait for a connection when dialing out. The two variables are #local-time and #ld-time; they default to 25 seconds and 50 seconds respectively. (The time used for long-distance (``ld'') dialing is longer because of delays in the phone system.) 6.2.4.4 A speed-up If you define the variable #hayes to be `1', then Fnordadel will blithely assume that the modem returns `3' for `NO CARRIER' and `7' for `BUSY' when it's dialing out. This is a useful kludge to speed up dialing out; otherwise, you've got to wait for the defined amount of time (see Section 6.2.4.3 [Timing], page 91) to pass before Fnordadel will realise that the call is not going to be successful. Please note that defining #hayes has no other effect; it will not cause Fnordadel to assume anything else about the nature of your modem. 6.3 High-Speed Modems Getting high-speed modems (9600 bps and up) to work with your system isn't quite as straight forward as with lower-speed units. For one thing, if you're using TOS 1.4 or higher, there is a glitch that prevents hardware (RTS/CTS) flow control from working. To fix the problem, you need to install tos14fx2.prg in your AUTO folder. See Section 13.1 [Things to Make Fnordadel Work or Work Better], page 151. For another thing, high-speed modems are typically able to talk to your Atari at a fixed speed (usually 19,200 bps), and handle the online user's varying connect speed themselves. To make this work properly, you don't want your Fnordadel to try altering the serial port speed; instead, you want it locked at a fixed setting. This is done by setting #sysbaud to the speed at which you wish the system locked, #searchbaud to `0', and all the result code strings to the null string, "". See Section 6.2.3.1 [Searchbaud], page 89, and Section 6.2.3.2 [Result codes], page 89. Two side-effects of port locking are that file transfer time estimates will be out of whack, and the `calllog.sys' file will show all users connected at the locked speed. These problems will be fixed some day. Chapter 6: Modem Stuff 92 6.4 Common Modem Problems o "The modem won't work properly at 2400 baud! Help!" See Section 6.2.3.3 [2400-baud operation], page 90. o "What happens if I turn the modem off while someone is online?" Nothing bad. Because you've got the #modemsetup string defined (you *have* got it defined, right? If not, see Section 6.2.2 [Initialisation], page 87), the BBS will simply detect the loss of carrier and immediately reinitialise the modem properly for the next caller, logging the previous caller off. o "My Blistering-Speed-of-Deth 153,600 baud modem won't work right with Fnordadel! Help!" Please send us two of the modems in question, and we promise to have Fnordadel working flawlessly with them right away!