page modified February 24, 2016

Legacy TNC-PI assembly instructions

This page has instructions for assembly of older Coastal Chipworks TNC-PI boards. Please see this page for instructions on the latest boards.

There are 3 models of the board. See TNC-PI General Information for details.

All three models may be assembled with the 10 pin JP2 header. Available here from SparkFun and included with the TARPN green-board TNC.

PCB boards v1.2, v2.0, and TARPN v2.1

Click to enlarge

The three models have the same parts designators in silkscreen so where parts are common between the three boards, they are labelled the same on each board. For the most part you can follow the instructions for the new 10-pin board and successfully build any of the 3 models. I have highlighted the board‑specific differences in the instructions.

Caveat: My instructions are written for an experienced kit-builder though this kit isn't particularly difficult compared to any other beginner kit. The issue is that I don't know all the things to advise you on up front and a beginner kit would have that kind of advice.
That said, I suggest you use a temperature controlled soldering iron, and rosin core lead solder, 60/40 or some such. Also, don't use flux on the board. Cleaning the board before or after soldering should not be necessary.
The part designations, like R1, U2, etc... are silkscreened on the top of the board. Insert all parts from the top of the board where the appropriate designator indicates. The photos provided may be helpful. Beware that there can be multiple versions of the board and the photos are only of one version. Use the silk-screen as the last word unless specifically directed NOT to in the text.
If there is a step which installs multiple parts, you can put all of the parts into the board in any order, and then solder all of them at once.

The reason for the step‑wise assembly order is so in each step when the board is flipped upside‑down for soldering the board doesn't rock too much, and for some steps you can take advantage of the table‑top to force the parts flush to the board for best mechanical stability. The test step, to assure proper voltage regulator function, is done as early as convenient.

What you will need

Appropriate Raspberry PI modified with 3 cuts on the header as shown here:
Power supply for the Raspberry PI to plug into the micro-USB socket.
Insulation Displacement Connector ribbon cable with 2 or more connectors to power up the TNC-PI.
Volt Ohm Meter to check the TNC-PI regulator
diagonal cutters

raspberry_pi_header_with_cuts_i6_07066x600

Some of the images on this page can be enlarged and opened in a new browser tab by clicking on them.

Install parts in this order:

1	X1	3.57 MHz crystal
2	X2	20.00 MHz crystal	Note: Make sure you place X2 into the PCB spot marked for it. There is a capacitor part which is the same footprint and adjacent to the crystal.

C2, C4, C5, C6,
C11, C14, C15, C21

0.1 f

Eight yellow non-polorized barrels

Skip this step for GREEN TNC kits.
Note: JP3 and JP4 holes are only present on very few early v1.x PCboards.
For boards where these four holes and silkscreen markings are present, install the two wire jumpers at this step.
Use wire trimmed from one of the yellow caps to create two separate jumpers short between lands.
The 10-pin header is installed later.

JP3 and JP4

scrap solid wire

short between holes for JP3 and JP4. See photo
2015_i6_05057__2x5_header

R14 is deleted from the TARPN v2.0, v2.1 and v2.2 PCboard.
Those kits would only have four 10k resistors.

R5, R11, R14,
R16, R18

10K resistor
R5_i6_07029x170

Brown, black, orange
R14, not shown, would be on the extreme left edge of the board near X2

R1, R2, R3

100K resistor
R1_i6_07034x170

Brown, black, yellow

R4, R17, R19

1K resistor
R4_i6_07036x170

Brown, black, red

24.9K resistor
R8_i6_07038x170

Red, yellow, white, red, brown

9.31K resistor
R9_i6_07041x170

White, orange, brown, brown, brown

R10

18.7K resistor
R10_i6_07042x170

Brown, grey, purple, red, brown

Inspect the soldering around R10 and make sure you do not have a short between R10 and R11

U2, U3
U4, U5

IC Sockets
One 16-pin, one 18-pin
and two 8-pin sockets

These are usually installed and soldered one at a time. You can either hold the socket with a finger while soldering the two corner pins in, then finish the rest of the pins, or you can insert the socket and then bend out two of the corner pins to hold it into place.
Be careful of the orientation.
They are not all pointing the same way!

Make sure you arrange the sockets so the divit at one end lines up with the markings on the PC board.
Note that some of the sockets are pointed opposite of some of the others. Do not install the ICs in the sockets at this point.

TX TEST

pushbutton, 4-pin
(green boards only)
pushbutton_part_i6_07047x340

Carefully wiggle the four pins through their holes. Don't put excess pressure else they bend and are hard to put back.

C9, C10

18 pf

ceramic disk

⇐ When stuffing the capacitors, direct the wires so they don't cross. This will enable you to solder the pads without shorting.

C12, C13

22 pf

ceramic disk

⇐ When stuffing the capacitors, direct the wires so they don't cross. This will enable you to solder the pads without shorting.

C7, C8

0.01 f 2.5%
C12_i6_07023

Red and yellow or grey; if grey marked 10 nF

100 pf

labelled 101
ceramic disk or dipped

10 f Polarized
electrolytic capacitor
C1_i6_07049x170

Part has stripe on one side with ‑ sign.
The other side lines up with + sign in the silkscreen.
C1_i6_07037x150

RX TEST

SPDT

slide switch, 3-pin. Orientation doesn't matter.
Red boards have no RX TEST switch.

PN2222 transistor

3-pin -- orientation is important! Line up part with silk-screen.
Do not confused with U1

Regulator MCP1700-33
or
MCP1700-30

3 pin
Install so the flat side is toward the edge of the board.
Note that the silkscreen is in error on TARPNv2.1 boards

JP2

2 x 5 header
J2_header_part_i6_07048x340

2x5 header is available at SparkFun for your 26 or 40 pin kit.
2x5 header is included included with TARPN 10-pin versions of the kit.

JP2 symbol is sometimes not visible
Insert on top, solder from bottom
For boards with 26 or 40 pin holes, install at the end of the board toward U1 regulator

tnc_pi_v1_2b_populated_2015_i6_05151x600

Note: 2x5

JP7

V1.1 Red board PCBs and some V1.2 Red board PCBs have a JP7 next to C1. Short this permanently with a loop of wire. This enables VCC to the board.

Power up and test voltage

Shutdown your Raspberry PI and remove its memory card. This will keep the file system on the card from getting corrupted if there is any debugging to be done.
Locate the largest IC socket on the board which is U3. It is 9 pins on a side.
Use a ribbon cable to connect the TNC-PI to a Raspberry PI. Make sure the ribbon is aligned so
pin 1 of the Raspberry PI is on the same end of the ribbon as pin 1 on the TNC-PI.
Power up the Raspberry PI without its memory card.
Use a voltmeter to check the voltage between the middle pin on one side of U3 and the middle pin
on the other side of U3, i.e. pins 5 and 14. The voltage difference between the two should be 3.3 volts.
Any voltages between 3.25 and 3.35 will do. Pin 5 is the negative side and pin 14 is the positive side.
We're really only interested that it is 3.3 volts.
Power off the Raspberry PI and disconnect the ribbon from the TNC-PI. Make sure you keep track of your memory card. You can put it back into the Raspberry PI.

If there is a problem, inspect the Regulator U1, capacitor C1 and the 10 pin header. Send an email on TARPN groups-io email reflector if you are still having an issue.

Remove power from the Raspberry PI.

Yellow LED (DCD)
d5_led_part_i6_07043x340

Polarized -- make sure the square end
lines up with the silkscreen. Ensure the shorter leads on the LEDs go through the holes closest to the flat side of the LED outline.

Red LED (PTT)
d4_red_led_part_i6_07044x340

Polarized -- make sure the square end
lines up with the silkscreen.

R6 and R7

10K trimmer potentiometer
R7_part_i6_07046x340

Orange or blue and white
Carefully wiggle the three pins through their holes. Don't put excess pressure else they bend and are hard to put back.
Green boards before V2.3 do not have R6.

DE-9 connector
de9_part_i6_07090x340

Push flush to the board. Solder the 2 large pin-pairs on the side holes first while forcing the connector solidly onto the board. This will give you the most robust connector.
Next solder the 9 small pins.

Install Integrated Circuits U2 through U5
You may wish to bend the pins of the four ICs slightly inward to facilitate inserting them into their sockets. Ensure the notch on the top of each chip lines up with the notch printed on the PC board. Also make absolutely certain that you do not mix up the two 8 pin chips and plug them into the wrong sockets.
28	U2	CML MX-614 Modem	16 pin IC
29	U3	PIC16F1847 microcontroller	18 pin IC
30	U4	MCP6023 Op Amp	8 pin IC
31	U5	23K640 Memory	8 pin IC

There is a 6 pin mostly-in-line set of holes marked ICSP (In Circuit Serial Programming) . These holes are left unconnected.

On some red boards there are unused pins marked J.

Power up CPU test

Shutdown your Raspberry PI and remove its memory card. This will keep the file system on the card from getting corrupted if the power is removed and re-applied arbitrarily.

Connect up the TNC-PI ribbon to the Raspberry PI, observing proper ribbon polarity.

While observing the the LEDs on the TNC-PI, apply power to the Raspberry PI. The RED and YELLOW LEDs should both illuminate, then the RED goes off, followed by the YELLOW. Some additional flickering may also be observed after the two LEDs first go out.

Congratulations. Youre done assembling the TNC-Pi.
Configure TNC-PI