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PMP -- Poor Man's Packet Version 1.1 A software TNC for the IBM PC. by Andrew C. Payne, N8KEI April, 1990 (last revised July, 1991) Disclaimer: No guarantees or warranties of any kind are expressed or implied. This program is supplied "AS IS" without any warranty of any kind, either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose. Neither the author nor anyone else who as been involved in the creation, production, or delivery of this program shall be liable for any direct, indirect, or consequential or incidental damages arising out of the use or inability to use this program. Copyright (c) 1990, 1991 Andrew C. Payne All rights reserved. TABLE OF CONTENTS ================= Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 Getting Started . . . . . . . . . . . . . . . . . . . . . . 5 Hardware Requirements . . . . . . . . . . . . . . . . . 5 Installing, Configuring, and Running PMP . . . . . . . 5 Configuration Commands . . . . . . . . . . . . . . . . 5 Using PMP . . . . . . . . . . . . . . . . . . . . . . . . . 10 Keyboard Commands . . . . . . . . . . . . . . . . . . . 10 Modem Interface . . . . . . . . . . . . . . . . . . . . . . 12 PMPTEST . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Commands . . . . . . . . . . . . . . . . . . . . . . . 13 Getting your modem to work with PMP . . . . . . . . . . 14 Introduction ============ What is PMP? PMP is a packet radio program that uses the software approach. In a nutshell, this means that the things that are normally done with hardware in a conventional TNC (Terminal Node Controller) are instead done with software in your computer. The advantage of this method is that most of the hardware of a normal TNC is no longer required. In simplifying the hardware, you lose some of the flexibility of a TNC. Who is PMP intended for? PMP is intended for anyone with an IBM PC type computer who wants to get into packet very inexpensively. PMP is perfect for someone who wants to get his/her feet wet before sinking a lot of money into equipment. PMP is also ideal for the scanner listener who wants to monitor packet but doesn't want to spend another scanner's worth of money. Because of the minimal hardware required, PMP is also good for portable setups. Modems can be constructed to actually fit inside VHF/UHF radios, eliminating the need for a separate TNC or modem box. What do I need to run PMP? PMP requires an IBM PC/AT/386/486 or compatible with at least 256K of memory and a parallel printer port (many video cards have a parallel port built in). You also need a Bell 202 type modem, VHF/UHF radio, and cables to connect everything up. Finally, you need the PMP software. What are the advantages of PMP over a "regular" TNC? The advantages of PMP are basically those outlined above: minimal hardware and low price. The only hardware required is a 1200 baud Bell 202 modem and cables to connect to the computer and radio. We have a single-chip design that fits on a 2 inch square board and costs less than $40. Also, this crystal controlled modem is a much better modem than those in many of the TNCs. What do I lose by using PMP instead of a TNC? PMP doesn't have all of the flexibility of a TNC. It runs on PCs ONLY. Also, since PMP is a program on your PC, you can't leave PMP on (to act as a digipeater, for example) without tying up your entire computer. Also, all of the packet software for the PC designed to work with TNCs (such as YAPP, the W0RLI BBS, and KA9Q's TCP/IP software) will not work with PMP. How was PMP developed? DIGICOM>64 for the Commodore 64 (which uses the same software approach) has been around for a while. With the popularity of DIGICOM>64 and the growing popularity of inexpensive IBM PC clones, we asked ourselves: "Has anyone done a DIGICOM>64-like program for the PC?" Some queries about such a program resulted in answers like: "Nope, never heard of such a thing. Sure would be a good idea though." At that point, we decided to start the PMP project. Kevin, WB2EMS, concentrated on the hardware design and Andy, N8KEI, developed the software. Within a few weeks, the first prototype modem was built, and two weeks after that PMP sending and receiving its first packets. I have some more questions. How can I get in touch with you? For software and general questions, problems, suggestions, or comments, write to: Andrew C. Payne, N8KEI Route 3, Box 78-Q Berkeley Springs, WV 25411 Or, if you have access to Internet e-mail, write to: payne@tcgould.tn.cornell.edu For hardware questions, problems, suggestions, or comments write to: Kevin Feeney, WB2EMS 468 Hines Road Ithaca, NY 14850 Also, write to Kevin for kit availability. Currently (July, 1991) we have TCM3105 modem chips, PC boards, and the miscellaneous parts needed to make a complete modem. Getting Started =============== Hardware Requirements --------------------- The following hardware is required to run PMP: - an IBM PC/XT/AT/386/486 or compatible with at least 256K RAM and a parallel printer port - a Bell 202 type 1200 baud modem - A VHF/UHF radio - cables to connect the printer port to the modem and the modem to the radio Installing, Configuring, and Running PMP ---------------------------------------- Installing PMP is very straightforward: only two files are required, one is optional: PMP.EXE The PMP program PMP.CFG The Configuration file PMPTEST.EXE (optional) An alignment/test program To install PMP on your system, copy these files to a floppy disk or a subdirectory on your hard disk. To start, just type 'PMP' from the DOS prompt and you should see the opening title screen in a few seconds. The configuration file, PMP.CFG, contains options and parameters specific to your packet station: your callsign, timing parameters, and other items described in detail below. The PMP.CFG file is a an ASCII text file which can be modified with any standard text editor (such EDLIN supplied with DOS). Lines that begin with a pound sign (#) are comments and are ignored. All other lines are configuration commands for PMP, listed below: Configuration Commands ---------------------- mycall <callsign> Sets your callsign in the form of N8KEI-XX, where XX is the SubStation Id (SSID). The SSID is used to differentiate between multiple stations with the same callsign (e.g. N8KEI, N8KEI-1, N8KEI-2, etc). The SSID ranges from 0 to 15, and 'N8KEI' and 'N8KEI-0' are equivalent. Your callsign MUST be correct before transmitting. txdelay <milliseconds> Sets the transmitter delay. This is the time PMP waits after keying the transmitter and before sending data. Slow transmitters (synthesized rigs, rigs with relays in the transmit path, etc) will require longer to stabilize after the transmit line is keyed. These slow rigs need a larger 'txdelay'. retry <#> Number of retries attempted before dropping a connection. If you are on a busy channel, you may want to increase this value from its default value (10) to prevent losing connections. frack <#> Number of seconds used to compute the round trip time before resending packet. If you are on a busy channel, you may want to increase this value. pthresh <#> Sets I-packet size threshold. This is an optimization that speeds up the AX.25 protocol for small packets. I-packets with data fields of smaller than 'pthresh' are resent (with no polling) when no ACK is received in the timeout period. Longer packets are polled a la standard AX.25 Level 2. check <#> Specifies the time-out value (in seconds) for the link keep- alive timer. After this many seconds of inactivity, PMP will poll the remote node. maxframe <#> Specifies the maximum number of frames allowed to be outstanding (e.g. un-acknowledged). This parameter must be between 1 and 7. On busy channels, a lower value is better. paclen <#> Specifies the maximum packet length in bytes. This parameter must be between 1 and 256. normal <#> bright <#> inverse <#> status <#> message <#> These commands set the attributes (colors) for normal text, bright text, inverse text, and the status line. If not specified, the attributes default to the attributes for a monochrome video system. An attribute consists of a code for a background color and a code for a foreground color: Color Foreground Background Black 0 0 Blue 1 16 Green 2 32 Cyan 3 48 Red 4 64 Magenta 5 80 Brown 6 96 Lightgray 7 112 Darkgray 8 - Lightblue 9 - Lightgreen 10 - Lightcyan 11 - Lightred 12 - Lightmagenta 13 - Yellow 14 - White 15 - To form the color attribute, just add the code for the foreground color to the code for the background color. Note that not all colors can be backgrounds. For example, for a white on red status line (attribute 15+64=79), use the configuration command: status 79 sound <#> Enables or disables sound. If <#> is non-zero, sound is enabled. If <#> is zero, sound is disabled. ctext <string> Specifies the welcome message to be sent when other stations connect to you. If no CTEXT is specified in the .CFG file, no welcome message is sent during incoming connects. Multiple CTEXT lines can be specified: all will be sent during incoming connects in the order they appear in the .CFG file. capture <#> Specifies the size (in bytes) of the capture memory buffer. Capture data is held in this buffer, then flushed to disk when the buffer fills. Smaller capture buffers will require more disk writes. On a floppy based systems, a large value is recommended to minimizes disk writes. This value should always be a multiple of 512 (the MS-DOS sector size). define <key> <definition> Defines a string associated with a function key. <key> is one of the function keys F1 through F8 (F9 and F10 are currently used for debug functions). <definition> is any string. Control characters may be imbedded in the <definition> string with the '^' character (e.g. '^M' is interpreted as a carriage return). ALT key sequences may be imbedded with the '~' character (e.g. '~c' is interpreted as ALT-C, the connect command). beacon <#> Specifies the beaconing interval, in seconds. Beacons (see 'btext', below) will be sent at the specified interval. A '0' value disables beaconing. btext <string> Specifies the text sent during beacons. baddr <string> Specifies the address (and path) to which beacons are sent. Digipeaters are allowed (e.g. "QST VIA W2CXM-1"). autowrap <#> Specifies the column number at which autowrap is active. Autowrap is a feature similar to most word processors where it is not necessary for the user to hit return after typing beyond a certain column; the line is automatically wrapped. A '0' value disables autowrap. pttport <port#> <bit> <level> txport <port#> <bit> cdport <port#> <bit> <level> rxport <port#> <bit> init <port#> <value> These configuration commands specify the ports and bits that PMP uses for the modem interface. The standard configuration file assumes values appropriate for the first parallel port, LPT1. You should not have to change these commands unless you are using PMP with LPT2 or are experimenting with a different modem interface. To reconfigure PMP for LPT2:, use these configuration commands: pttport 0x278 2 0 txport 0x278 1 cdport 0x279 0x80 0 rxport 0x279 8 <port#> specifies the port number in the PC's I/O space. <bit> is a bit mask to specify the particular bit of the port (e.g. 1 for bit 0, 2 for bit 1, 4 for bit 2, etc). <level> specifies the active level for the signal: 1 for active high, 0 for active low. 'pttport' (output) defines the port PMP uses to make the radio transmit. 'cdport' (input) defines the carrier detect line. 'txdata' (output) and 'rxdata' (input) define the output and input data lines. Note that no active levels are specified for these signals: the data lines are edge-sensitive, not level-sensitive. The 'init' command specifies any port initializations (e.g. to enable mini-modems powered from spare output bits). At start up, PMP writes the specified <value> to the specified <port#>. Sample PMP.CFG file: # # This is a sample PMP.CFG file # mycall N8KEI-2 txdelay 300 retry 12 frack 3 pthresh 15 sound 1 ctext Hello from Andy in Berkeley Springs, WV. ctext If I'm not around, please leave a message. btext N8KEI, QTH Berkeley Springs, WV baddr QST VIA W2CXM-1 beacon 300 define f1 ~cwb2ems-1^m # # End of sample file # All options in PMP.CFG default to reasonable values if they are not specified in the file. However, a MYCALL parameter must always be present to set your callsign correctly. Using PMP ========= After starting PMP (by typing 'PMP' at the DOS prompt), you should see an opening title screen (with current version number). Press any key to advance from this screen to the main screen. The main screen is divided into three areas. Most of the upper part of the screen is the incoming data area; incoming data and packets are displayed here. The second to last line on the screen is the data entry line; everything you type for transmission is entered here. The bottom line of the screen is the highlighted status line, which has the following items (from left to right): - The version number - Your callsign (make sure this is correct before transmitting) - The current connect path (blank if currently not connected) - Outstanding packet bar, there will be an asterisk (*) on this bar for each outstanding packet (a packet that has been sent but not acknowledged by the other station) This bar will be blank if currently not connected. - TX/RX status lights. This status indicators will light when PMP is transmitting or receiving packets. Keyboard Commands ----------------- Most commands in PMP are ALT key combinations (formed by holding down the ALT key and some other key), listed below: ALT-C Connect to another station. You will be prompted for the connect station and path in the form: WB2EMS VIA W2CXM-1,WB2TVB Press ESC to abort the connect attempt. ALT-D Starts a disconnection. If the remote node is not responding to the disconnect request, press ALT-D again to force a disconnect. ALT-B Sends a beacon packet (with the text specified in the 'btext' parameter in the configuration file). ALT-H Shows a help screen, listing all keyboard commands. ALT-J Screen snapshot. Writes the current screen to a text file. ALT-N Nodes recently heard. Nodes are listed starting with the most recently heard. Information listed for each node includes the callsign of the node, the time last heard, the number of packets heard, and the protocol types used by the node. ALT-P Pause (hold) the screen. After pausing, press any key to resume. ALT-S Shows the status of PMP: the number of packets sent and received, error counts, number of bytes free, etc. ALT-X Exits to DOS. ALT-U Text file upload. You will be prompted for the name of an ASCII file to send across a currently connected link. ALT-L Toggle text file capture/download. You will be prompted for a file to log all received data. "Cap" will appear on the status line, indicating that a capture is in progress. Press ALT-L again to stop capturing and close the file. UP & DOWN The [Up] and [Down] arrows can be used to move forward and backward to review data that has scrolled off the top of the screen. [PgUp] and [PgDn] will page through the scrollback buffer a screenfull at a time. F1-F4 User defined function keys. Sends the string defined for the key (see 'define' in the configuration commands). Modem Interface =============== PMP interfaces to the external modem (and radio) through the PC's parallel port. PMP uses two output pins and two input pins which are connected as follows: Parallel Port Pin Signal Dir. Description ----------------------------------------- 2 TXD Out Transmitted data. 3 PTT Out Push-to-talk, active-high. Keys the radio to transmit. 11 CD In Carrier detect, active-high. Goes active when a packet signal is detected. 15 RXD In Receive data. 25 Gnd Gnd Signal ground. The PMPTEST utility is very useful for testing the parallel port and modem interface (see next section for more information). On most PCs, the parallel port is a female DB-25 type connector and uses standard TTL levels. We have developed a small, inexpensive, two-chip modem that works well with PMP. For details, see the August, 1991 issue of 73 Magazine (pages 8-14). PMPTEST Utility =============== PMPTEST is a utility program that aids in testing the parallel port and modem interface (see MODEM INTERFACE). PMPTEST is started by typing 'PMPTEST' from the DOS prompt. At present PMPTEST works only with modems interfaced to LPT1:. Across the bottom of PMPTEST's screen are four indicators: Carrier Detect (CD) Indicates the current input level of the Carrier Detect line. Receive Data (RXD) Indicates the current input level of the Receive Data line. Transmit Data (TXD) Indicates the current output level of the Transmit Data line. Push To Talk (PTT) Indicates the current output level of the Push To Talk line. Commands -------- PMPTEST has several commands: [ESC] Exits program. [SPACE] Toggles transmit (PTT) line. The current transmit status will be indicated with the PTT indicator. [F2] On-air modem alignment mode. (see below) [F3] Toggle transmit data level. The current transmit level is indicated with the TXD indicator. [F5] Transmits a 600hz test signal. PTT will be set high, and the transmit data will be toggled at 600hz. Any key will cancel the test. [F6] Loopback alignment (currently not implemented). Getting your modem to work with PMP ----------------------------------- This section describes some simple tests using PMPTEST. Carrier Detect Adjust your radio and modem so that the Carrier Detect accurately reflects channel activity. The CD status light should indicate channel activity. Receive Data The RD indicator should flicker (on and off) when data is being received. PTT Use the [SPACE] bar to toggle the transmit on and off. Your radio should start transmitting when PTT goes high and stop transmitting when PTT goes low. Transmit Data Use the [SPACE] bar to toggle your radio into transmit mode and use the [F2] key to toggle the transmit data. Your radio should transmit a high or low tone, depending on the transmit data level. Receive Alignment Many modems (including our design) have a receive section that must be properly aligned. Tune your radio to a busy packet channel, and make sure that the Carrier Detect and Receive Data lines are functioning (as described above). Use [F1] to enter the alignment mode. As each packet is received, it's timing will be analyzed and two error percentages will be displayed on the screen. Adjust your modem so that these two numbers are as close to zero as possible: between -5% and +5% is ideal. Use long packets to make your adjustments; short packets or noise bursts will give inaccurate error readings.