Building a 4 Port Packet Controller

Introduction

This page serves to be a guide for those wishing to build a 4 port packet controller on a Raspberry Pi 3 or similar hardware. This design allows any combination of software TNC (Direwolf or G8BPQ's QtSoundModem) or G8BPQ's C port of ARDOP modem for HF. This means the controller can have any combination of 300/1200/2400/4800/9600 baud packet and/or ARDOP modems running simultaneously. When coupled with G8BPQ's excellent packet switch, this allows for a low cost controller to house a multiport packet system or to act as a "network TNC" for other software, including Outpost PPM, Winlink Express, BPQ32 on Windows and others which support the AGWPE and/or KISS over TCP protocols. It uses the very popular Linksys WRT54G or BEFSR41 router as an enclosure as well as acts as a 3 or 4 port 10/100 megabit network switch to allow expansion of controllers and/or addition of other network devices. When coupled with a WRT54G, this can also include providing a wireless access point or if flashed with DD-WRT firmware, bridging to a wireless access point (Wireless client). This should cost under $100 USD to build, most of the part values are not critical.

Parts list:

1x 24x12 hole perf board
4x 10k 1/4w resistors
4x 2n2222 Transistor or equivalent
4x 1n4004 Diode or similar
8x 50K Potentiometer
4x 10uF Electrolytic Capacitor
4x USB Soundcards
2-3ft of Ribbon cable, multicolor suggested
4x 18" Devicenet 2PR22 or equivalent cable
1x Raspberry Pi 3B or 3B+
1x 12VDC to 5VDC downconverter
1x WRT54G versions v2.0 or above or BEFSR41 v4.0 or above
8-12" of 22awg solid wire (Petsafe or equivalent)
1/8" Heatshrink tubing
1/4" Heatshrink tubing
9/64ths or 5/16ths inch drill bit and drill
1x RJ-45 connector and 6-8" of CAT-5 type cable
4x DB9 solder type female connector
4x DB9 Hoods, metal plated recommended

Assembly

1) Starting with a 24x12 hole perf board, take one of the 2n2222 transistors and place it 8 holes back and with pin 1 (emitter) 4 holes in from the left
File:1st 2n2222.jpg
2) Take one of the 1n4004 diodes and on the ringed side, bend the lead 180 degrees downward
File:1n4004 bend.jpg
3) Insert the 1n4004 diode directly behind the 2n2222 with it's anode (no stripe) directly behind the 2n2222 emitter and it's cathode (striped, bent 180 degrees) behind the 2n2222 base (center pin)
File:1n4004 with 2n2222.jpg
4) Take one of the 10K resistors and bend one lead 180 degrees, similar to the 1n4004 in step 2
File:10k bend.jpg
5) Insert the 10k resistor where the long lead goes through the same hole as the 2n2222 base (center pin) and the resistor itself goes through the pin one hole away from the 2n2222
File:10k to 2n2222.jpg
6) Flip the perf board over, bend the 2n2222 emitter, base leads towards the back of the board and the collector lead towards the front of the board. Bend both the thicker leads of the 1n4004 diode towards the front of the board. Bend the lead of the 10K resistor that shared a hole with the 2n2222 base backwards and the other lead of the 10K resistor forward.
File:Lead bends.jpg
7) Take the 10K resistor lead which was bent forward and feed it back up through the perf board to the top (component side)
File:10k lead up.jpg
8) Take the collector lead from the 2n2222 and feed it back up through the perf board to the top similarly to the 10K resistor
File:2n2222 collector lead up.jpg
9) Take the anode side of the 1n4004 (no stripe) and feed it's lead through the same row of holes in the perf board to the top as the 2n2222 collector
File:1n4004 anode lead up.jpg
10) Flipping the perf board back to the component side, bend all leads towards the front of the board. File:Leads forward.jpg
11) Flipping the perf board over to the lead side, apply solder to the junction of the 1n4004 anode and 2n2222 emitter as well as the junction of the 1n4004 cathode and 2n2222 base+10K resistor.
File:Solder junctions.jpg
12) Using wire cutters, carefully clip the excess leads on either side of the 1n4004 cathode, 2n2222 base and 10K resistor (center most junction). Do not trim the lead coming off the 1n4004 cathode and 2n2222 emitter, we will need it for connection to ground in a future step. File:Soldered junctions trimmed.jpg
13) Flipping the perf board back over, trim the diode, resistor and 2n2222 leads to be just long enough to go over the next hole towards the front of the perf board
File:Topside lead trim.jpg
14) Skip one hole to the right and repeat the assembly of the 2n2222, 1n4004 and 10K resistor (Steps 1-13). Be careful to not trim the lead on the underside for the 1n4004 cathode and 2n2222 emitter. File:Second PTT circuit.jpg
15) Repeat steps 1-14 for the remaining 2 PTT circuits, when finished it should look similar to this.
File:4 PTT circuit top.jpg[[File:4_PTT_circuit_bottom.jpg
16) Take one of the 50K potentiometers and bend the wiper pin back towards the other two pins. The original is on the left, the bent is on the right
File:Potentiometer pin bend.jpg
17) Insert the poteniometer at the back of the perf board, one row of pins from the rear all the way to the left.
File:Potentiometer in board.jpg
18) Flipping the board over, bend the outer most lead towards the front of the board and the wiper and inner leads towards the rear of the board
File:Potentiometer lead bend.jpg
19) Repeat steps 16-18 for the 7 remaining potentiometers, when finished it should look similar to this.
File:8 Potentiometers top.jpgFile:8 Potentiometers bottom.jpg 20) Take a 4 conductor ribbon cable and cut it to about 4-5/8" length. File:4 Conductor ribbon cut.jpg
In this guide the color map is

Purple: TX Audio
Blue: PTT
Green: RX Audio
Yellow: Ground

21) Strip back about 1/4" from the purple lead and 3/16" from the green lead, twist and tin with solder. File:Purple Green stripped tinned.jpg
22) Inserting the purple wire through the perf board, bend towards the 50K potentiometer furthest from the PTT circuits. This lead will need to overlap with the lead from the 50K potentiometer, if the wire is too short, pull it back out and strip a bit more insulation and try again. Once long enough, solder the purple lead to the 50K potentiometer. File:Purple to potentiometer.jpg
23) Inserting the green wire throught he perf board, bend towards the wiper of the adjacent potentimeter where we just soldered the purple wire. This lead does not need to be as long, just long enough to overlap with the wiper lead. Once bent and sufficient length is verified, solder the green lead to the 50K potentiometer wiper. File:Green to potentiometer.jpg
24) Pull the blue and yellow wires down to the lead side of the perf board. They will be attached in a future step. File:Blue and yellow lead side.jpg
25) Repeat steps 20-24 for the next 4 conductor ribbon cable, when finished it should look similar to this.
File:2 4 conductor ribbons top.jpgFile:2 4 conductor ribbons bottom.jpg
26) Repeat steps 20-24 for the 2 remaining 4 conductor ribbon cables, when finished it should look similar to this.
File:4 4 conductor ribbons top.jpgFile:4 4 conductor ribbons bottom.jpg
27) Take one of the USB soundcards and carefully begin to pry apart it's shell. A box cutter or similar knife along the groove seems to work well. File:Opening usb soundcard.jpg[[File:USB_soundcard_shellremoved.jpg
28) Flipping the USB soundcard over, using a pair of needle nose pliars and a soldering iron, carefully heat the audio connectors and gently pull them away from the soundcard. It will probably take a few times rotating between pins, but it should eventually pull off the board. File:Audio jack removal.jpgAudio_jack_removed.jpg
29) Repeat this process for the other jack on the soundcard, when complete the card should look similar to this.
File:Soundcard jacks removed.jpg
30) Apply solder to the 2 solder pads furthest from the USB connector on the microphone side and center most pin on the speaker/phone side.
File:Soundcard with solderpads.jpg
31) Take one of the 10uF electrolytic capacitors and solder it to the outer most pad on the microphone connector. Be sure to have the side with arrow pointing away from the pad. This is to block a small DC bias which is commonly present on the microphone line on soundcards. When completed it should look similar to this.
File:Soundcard with cap.jpg
32) Bend the axial lead of the capacitor 180 degrees back towards the soundcard. File:Soundcard capacitor lead bend.jpg
Once the lead is bent over the soundcard, cut the lead to be just short of the soundcard itself.
33) Repeat steps 27-32 for the remaining 3 soundcards.
File:Soundcards with capacitors.jpg
34) Take a 3 conductor ribbon cable and cut it to about 6-3/4" length. File:3 Conductor ribbon cut.jpg

In this guide the color map is

Red: Microphone Input
Orange: Ground
Yellow: Speaker output
35) Strip about 1/4" of the Red wire, twist and tin, then insert into the outer most potentiometer next to the green lead. Once overlap with the potentiometer lead is confirmed solder into place.
File:Red wire to potentiometer.jpg
36) Strip back about 3/16" of the yellow wire, twist and tin, then insert into the wiper of the outer most potentiometer wiper next to the purple lead. Once overlap with the potentiometer wiperis confirmed, solder into place.
File:Yellow wire to potentiometer wiper.jpg

The 3 conductor ribbon cable should look like this from the top of the perf board. File:3 Conductor ribbon top.jpg
37) Repeat steps 34-36 for the second 3 conductor ribbon cable cut to about 6-1/4" length to the next set of potentiometer. The third ribbon should be cut to about 5-3/4" and fourth ribbon should be cut to about 5-1/4". When finished it should look similar to this.
File:4 3 Conductor bottom.jpgFile:4 3 Conductor top.jpg
38) Flipping the perf board over to the lead site, pull the blue wire from the 4 conductor ribbon cable through the gap on the 3 conductor ribbon and pull it forward towards the front of the board
File:Blue wires through 3 conductor.jpg
39) Cut about 4-1/2" of the 22awg solid insulated wire for use as a ground bus wire. File:Ground bus wire.jpg
40) Strip back about 1" of insulation off one end and lay the ground bus wire along the perf board. We want it to run along right next to the 50K potentiometers which do not have wires soldered to them as well as the 2n2222 emitter lead tails we left from previous steps. Using a box cutter or similar, cut the insulation to length which shields the bus wire, but exposes the wire where solder connections need to be made. File:Ground bus wire cut1.jpg
41) Once the insulation is cut, pull the insulation away to expose the wire to each point that needs soldered.
File:Ground bus wire cut2.jpg
42) Repeat cuts of the insulation to allow connections to all potentiometers and other ground leads.
File:Ground bus wire cut3.jpg
43) Carefully apply solder to each junction where a ground connection is to be made. The first connection should look similar to this.
File:Ground bus wire solder1.jpg
44) The third junction is both the potentiometer as well as the 2n2222 lead. Bend the 2n2222 lead over the bus wire before applying solder.
File:Ground bus wire 2n2222 lead before solder3.jpgFile:Ground bus wire 2n2222 lead with solder4.jpg
45) Continue soldering the ground leads and potentiometer, the finished soldering should look similar to this.
File:Ground bus wire solder finished.jpg
46) Bend the ground bus wire at a right angle, towards the front of the perf board.
File:Ground bus wire bent.jpg
47) Strip back insulation to where the ground bus wire is exposed along the same row of holes with all the other PTT circuit leads.
File:Ground bus wire end stripped.jpg
48) Pull the exposed ground bus wire through the perf board to the component side.
File:Ground bus wire through board bottom.jpgFile:Ground bus wire through board top.jpg
49) Flipping the board over to the lead side, attach stripped insulation to the exposed bus wire and bend it towards the front of the perf board. File:Ground bus wire insulated bent.jpg

There is one point where the exposed bus wire is close to a 1n4004 cathode, 2n2222 base and 10K resistor lead. Be sure to leave sufficient space, slightly bending the ground bus wire if needed.
File:Ground bus wire spacing.jpg

50) Strip about 3/16" of insulation off the orange and yellow wires on the first couple of potentiometers, twist and tin the leads.
File:Orange and yellow stripped tinned.jpg
51) Cut about 3/8" of 1/8" heat shrink tube and slide it over the yellow wire, bend the orange and yellow wires together and solder them together.
File:Orange and yellow heatshrink solder.jpg
52) Slide the 1/8" heat shrink tube over the soldered junction, apply heat with a heat gun, hair dryer or similar to shrink the tubing over the soldered juction.
File:Orange and yellow heatshrunk.jpg
53) Repeat steps 50-52 for the three remaining wire pairs, when finished it should look similar to this.
File:Orange and yellow all complete.jpg
54) On the first 3 conductor ribbon cable, pull apart the 3 wires, strip about 3/16", twist and tin each wire.
File:3 conductor split tinned.jpg
55) Solder the red wire to the electrolytic capacitor, the yellow wire to the inner solder pad which has solder added and yellow wire to the inner speaker output pad.
File:3 conductor soldered to soundcard.jpg
56) Repeat steps 54-55 for the remaining three soundcards.
File:3 conductor to soundcard.jpg
57) Cut about 2 1/2" of orange wire, strip back about 3/16", twist and tin one end.
File:PTT1 GPIO wire prepared.jpg
58) Insert the tinned wire into the perf board adjacent to the first 10K resistor lead.
File:PTT1 GPIO wire inserted bottom.jpg
59) Bend the lead towards the back of the board, overlapping with the 10K resistor lead.
File:PTT1 GPIO wire bent top.jpg
60) Apply solder to this overlap, soldering the first orange wire to the 10K resistor lead.
File:PTT1 GPIO wire soldered.jpg
61) Cut about 1" of orange wire, strip back about 3/16", twist and tin one end.
File:PTT1 input wire prepared.jpg
62) Insert the tinned wire into the perf board adjacent to the 2n2222 lead.
File:PTT1 input wire inserted bottom.jpg
63) Bend the leads towards the back of the board, overlappign with then 2n2222 lead.
File:PTT1 input wire bent top.jpg
64) Apply solder to this overlap, soldering the second orange wire to the 2n2222 lead.
File:PTT1 input wire soldered.jpg
65) Strip the ends of the 1" second orange and neighboring blue wire, twisting and tinning the leads.
File:Orange and blue stipped tinned.jpg
66) Cut about 3/8" of the 1/8" heat shrink tubing and slide over the orange wire, solder the second orange wire to the neighboring blue wire.
File:Orange and blue soldered.jpg
67) Slide the heatshrink over the soldered junction and apply heat to shrink the heatshrink tubing over the junction.
File:Orange and blue soldered heatshrink.jpg
68) Repeat 58-67 using about 3" of red wire for the second circuit, 3-1/2" of brown wire for the third circuit and 4" of white wire for the third circuit. When finished it should look similar to this.
File:PTT wires finished.jpg
69) Cut about 2" of black wire, strip back about 3/16", twist and tin one end. Insert in the hole adjacent to the ground bus wire.
File:Ground wire inserted bottom.jpg
70) Bend the tinned black wire lead towards the back of the perf board, overlapping with the copper ground bus wire, apply solder to the junction.
File:Ground wire soldered.jpg
71) Take one of the 18" Devicenet cable and strip back about 5/8" of the outer jacket.
File:Devicenet 5-8in measure.jpgFile:Devicenet 5-8in cut.jpgFile:Devicenet 5-8in jacket remove.jpg
72) Fold back the braid on the Devicenet cable.
File:Devicenet braid folded back.jpg
73) Carefully pull the nylon threads from the bundle and cut away the threads.
File:Devicenet thread cut.jpg
74) Separate the red/black and blue/white pairs and bare ground wire.
File:Devicenet separated pairs ground.jpg
75) Carefully peel away the foil surrounding the red/black pair, a small cut in the foil may be needed to begin peeling away. Repeat this for the blue/white pair as well
File:Devicenet foil removal.jpg
76) Separate all wires in the Devicenet cable bundle.
File:Devicenet wire separation.jpg
77) Strip back about 1/8" of insulation from the red, black and blue wires, twist and tin along with the bare ground wire. Do not strip back any insulation on the white wire.
File:Devicenet wire strip tin.jpg
78) Pull apart all wires on the first 4 conductor cable, strip back about 3/16" of each wire, twist and tin the leads. Cut about 1" of 1/4" heat strink tubing and slide it over the 4 conductor cable. File:4 conductor stripped tinned with heatshrink.jpg
79) Cut 4 sections of 1/8" heatshrink tubing, sliding the first section over the red wire of the devicenet cable, solder the red devicenet cable to the purple ribbon cable.
File:Devicenet red to purple ribbon.jpg
80) Slide 1/8" heatshrink tubing over the black wire, solder the black devicenet cable to the blue ribbon cable.
File:Devicenet black to blue ribbon.jpg
81) Slide 1/8" heatshrink tubing over the blue wire, solder the blue devicenet cable to the green ribbon cable.
File:Devicenet blue to green ribbon.jpg
82) Slide 1/8" heatshrink tubing over the bare wire, solder the bare wire from the devicenet cable to the yellow ribbon cable.
File:Devicenet bare to yellow ribbon.jpg
83) Cut about 5/8" of 1/8" heatshrink tubing over the yellow wire, leaving some heatshrink past the end of the white wire and slide the other heatshrink tubing over the junction of the 4 soldered wires.
File:Devicenet to ribbon with heatshrink.jpg
84) Apply heat to the 1/8" heatshrink tubing, to cover the soldered junctions and end of the white wire.
File:Devicenet ribbon heatshrink applied.jpg
85) Carefully pinch the heatshrink which runs past the tip of the white wire. This will be hot from the heat gun so be careful.
File:Devicenet white wire heatshrink pinch.jpg
86) Pull all wires together and squeeze gently, slide the 1/4" heatshrink tubing over the bundle of soldered wires.
File:Devicenet 1-4in heatshrink1.jpgFile:Devicenet 1-4in heatshrink2.jpg
87) Apply heat to the 1/4" heatshrink to insulate the bundle of soldered wires.
File:Devicenet ribbon heatshrink applied.jpg
88) Wrap electrical tape starting over the heatshrink, wrapping past the folded back braid of the devicenet cable.
File:Deviecnet ribbon electrical tape.jpg
89) Repeat steps 71-88 for the remaining three devicenet cables. When finished it should look like this.
File:Devicenet ribbon complete.jpg
90)