Based on kernel version 3.19. Page generated on 2015-02-13 21:21 EST.
1 This is the 6pack-mini-HOWTO, written by 2 3 Andreas Könsgen DG3KQ 4 Internet: firstname.lastname@example.org 5 AMPR-net: email@example.com 6 AX.25: dg3kq@db0ach.#nrw.deu.eu 7 8 Last update: April 7, 1998 9 10 1. What is 6pack, and what are the advantages to KISS? 11 12 6pack is a transmission protocol for data exchange between the PC and 13 the TNC over a serial line. It can be used as an alternative to KISS. 14 15 6pack has two major advantages: 16 - The PC is given full control over the radio 17 channel. Special control data is exchanged between the PC and the TNC so 18 that the PC knows at any time if the TNC is receiving data, if a TNC 19 buffer underrun or overrun has occurred, if the PTT is 20 set and so on. This control data is processed at a higher priority than 21 normal data, so a data stream can be interrupted at any time to issue an 22 important event. This helps to improve the channel access and timing 23 algorithms as everything is computed in the PC. It would even be possible 24 to experiment with something completely different from the known CSMA and 25 DAMA channel access methods. 26 This kind of real-time control is especially important to supply several 27 TNCs that are connected between each other and the PC by a daisy chain 28 (however, this feature is not supported yet by the Linux 6pack driver). 29 30 - Each packet transferred over the serial line is supplied with a checksum, 31 so it is easy to detect errors due to problems on the serial line. 32 Received packets that are corrupt are not passed on to the AX.25 layer. 33 Damaged packets that the TNC has received from the PC are not transmitted. 34 35 More details about 6pack are described in the file 6pack.ps that is located 36 in the doc directory of the AX.25 utilities package. 37 38 2. Who has developed the 6pack protocol? 39 40 The 6pack protocol has been developed by Ekki Plicht DF4OR, Henning Rech 41 DF9IC and Gunter Jost DK7WJ. A driver for 6pack, written by Gunter Jost and 42 Matthias Welwarsky DG2FEF, comes along with the PC version of FlexNet. 43 They have also written a firmware for TNCs to perform the 6pack 44 protocol (see section 4 below). 45 46 3. Where can I get the latest version of 6pack for LinuX? 47 48 At the moment, the 6pack stuff can obtained via anonymous ftp from 49 db0bm.automation.fh-aachen.de. In the directory /incoming/dg3kq, 50 there is a file named 6pack.tgz. 51 52 4. Preparing the TNC for 6pack operation 53 54 To be able to use 6pack, a special firmware for the TNC is needed. The EPROM 55 of a newly bought TNC does not contain 6pack, so you will have to 56 program an EPROM yourself. The image file for 6pack EPROMs should be 57 available on any packet radio box where PC/FlexNet can be found. The name of 58 the file is 6pack.bin. This file is copyrighted and maintained by the FlexNet 59 team. It can be used under the terms of the license that comes along 60 with PC/FlexNet. Please do not ask me about the internals of this file as I 61 don't know anything about it. I used a textual description of the 6pack 62 protocol to program the Linux driver. 63 64 TNCs contain a 64kByte EPROM, the lower half of which is used for 65 the firmware/KISS. The upper half is either empty or is sometimes 66 programmed with software called TAPR. In the latter case, the TNC 67 is supplied with a DIP switch so you can easily change between the 68 two systems. When programming a new EPROM, one of the systems is replaced 69 by 6pack. It is useful to replace TAPR, as this software is rarely used 70 nowadays. If your TNC is not equipped with the switch mentioned above, you 71 can build in one yourself that switches over the highest address pin 72 of the EPROM between HIGH and LOW level. After having inserted the new EPROM 73 and switched to 6pack, apply power to the TNC for a first test. The connect 74 and the status LED are lit for about a second if the firmware initialises 75 the TNC correctly. 76 77 5. Building and installing the 6pack driver 78 79 The driver has been tested with kernel version 2.1.90. Use with older 80 kernels may lead to a compilation error because the interface to a kernel 81 function has been changed in the 2.1.8x kernels. 82 83 How to turn on 6pack support: 84 85 - In the linux kernel configuration program, select the code maturity level 86 options menu and turn on the prompting for development drivers. 87 88 - Select the amateur radio support menu and turn on the serial port 6pack 89 driver. 90 91 - Compile and install the kernel and the modules. 92 93 To use the driver, the kissattach program delivered with the AX.25 utilities 94 has to be modified. 95 96 - Do a cd to the directory that holds the kissattach sources. Edit the 97 kissattach.c file. At the top, insert the following lines: 98 99 #ifndef N_6PACK 100 #define N_6PACK (N_AX25+1) 101 #endif 102 103 Then find the line 104 105 int disc = N_AX25; 106 107 and replace N_AX25 by N_6PACK. 108 109 - Recompile kissattach. Rename it to spattach to avoid confusions. 110 111 Installing the driver: 112 113 - Do an insmod 6pack. Look at your /var/log/messages file to check if the 114 module has printed its initialization message. 115 116 - Do a spattach as you would launch kissattach when starting a KISS port. 117 Check if the kernel prints the message '6pack: TNC found'. 118 119 - From here, everything should work as if you were setting up a KISS port. 120 The only difference is that the network device that represents 121 the 6pack port is called sp instead of sl or ax. So, sp0 would be the 122 first 6pack port. 123 124 Although the driver has been tested on various platforms, I still declare it 125 ALPHA. BE CAREFUL! Sync your disks before insmoding the 6pack module 126 and spattaching. Watch out if your computer behaves strangely. Read section 127 6 of this file about known problems. 128 129 Note that the connect and status LEDs of the TNC are controlled in a 130 different way than they are when the TNC is used with PC/FlexNet. When using 131 FlexNet, the connect LED is on if there is a connection; the status LED is 132 on if there is data in the buffer of the PC's AX.25 engine that has to be 133 transmitted. Under Linux, the 6pack layer is beyond the AX.25 layer, 134 so the 6pack driver doesn't know anything about connects or data that 135 has not yet been transmitted. Therefore the LEDs are controlled 136 as they are in KISS mode: The connect LED is turned on if data is transferred 137 from the PC to the TNC over the serial line, the status LED if data is 138 sent to the PC. 139 140 6. Known problems 141 142 When testing the driver with 2.0.3x kernels and 143 operating with data rates on the radio channel of 9600 Baud or higher, 144 the driver may, on certain systems, sometimes print the message '6pack: 145 bad checksum', which is due to data loss if the other station sends two 146 or more subsequent packets. I have been told that this is due to a problem 147 with the serial driver of 2.0.3x kernels. I don't know yet if the problem 148 still exists with 2.1.x kernels, as I have heard that the serial driver 149 code has been changed with 2.1.x. 150 151 When shutting down the sp interface with ifconfig, the kernel crashes if 152 there is still an AX.25 connection left over which an IP connection was 153 running, even if that IP connection is already closed. The problem does not 154 occur when there is a bare AX.25 connection still running. I don't know if 155 this is a problem of the 6pack driver or something else in the kernel. 156 157 The driver has been tested as a module, not yet as a kernel-builtin driver. 158 159 The 6pack protocol supports daisy-chaining of TNCs in a token ring, which is 160 connected to one serial port of the PC. This feature is not implemented 161 and at least at the moment I won't be able to do it because I do not have 162 the opportunity to build a TNC daisy-chain and test it. 163 164 Some of the comments in the source code are inaccurate. They are left from 165 the SLIP/KISS driver, from which the 6pack driver has been derived. 166 I haven't modified or removed them yet -- sorry! The code itself needs 167 some cleaning and optimizing. This will be done in a later release. 168 169 If you encounter a bug or if you have a question or suggestion concerning the 170 driver, feel free to mail me, using the addresses given at the beginning of 171 this file. 172 173 Have fun! 174 175 Andreas