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page modified March 24, 2016

TNC-PI Kit Ordering and Assembly

This page details the assembly of the TARPN version of the TNC-PI kit Rev 2.3. Other TNC-PI versions, see this page.
The TNC Printed Circuit Board should be labelled Rev 2.3 or 2.3a.
tncpi_v2_3_identification_expansion
If your board has a different silkscreen, see this page.
The TNC-PI is designed, packaged, and sold as a kit by Coastal Chipworks.
See below for a link to purchase the TARPN-tailored version of the TNC from Coastal. The TARPN-tailored kit is shipped with the 10-pin header and with a CPU preconfigured for I2C operation as per TARPN setup instructions.
See the Coastal Chipworks webpage for generic TNC-PI.

Buy the TARPN Version of the TNC-Pi Kit with preconfigured I2C mode
$43 each plus shipping

from Coastal Chipworks
in Fredonia NY

assembled_tarpnv2_1tncpi_i6_07179x261 allparts_i6_07103x800

This kit isn't particularly difficult compared to any other beginner kit.

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.

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
x1_i6_07056x200 XTAL_i6_07060
x1_on_v2_3_boardx600
2 X2 20.00 MHz crystal
X2_i6_07059x200 XTAL_i6_07060
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.
x2_on_v2_3_boardx600

3 C2, C4, C5, C6,
C11, C14, C15, C21
0.1 f
c2_parts_i6_07108x180
Eight yellow non-polorized barrels
c2_on_v2_3_boardx600

4 R5, R11, R14,
R16, R18
10K resistor
r5_parts_x170
Brown, black, orange
r5_on_v2_3_boardx600

5 R1, R2, R3 100K resistor
R1_i6_07034x170>
Brown, black, yellow
r1_on_v2_3_boardx600

6 R4, R17, R19 1K resistor
R4_i6_07036x170
Brown, black, red
r4_on_v2_3_boardx600

7 R8 24.9K resistor
R8_i6_07038x170
Red, yellow, white, red, brown
r8_on_v2_3_boardx600

8 R9 9.31K resistor
R9_i6_07041x170
White, orange, brown, brown, brown
r9_on_v2_3_boardx600

9 R10 18.7K resistor
R10_i6_07042x170
Brown, grey, purple, red, brown
r10_on_v2_3_boardx600
Inspect the soldering around R10 and make sure you do not have a short between R10 and R11
10 U2, U3
U4, U5
IC Sockets
One 16-pin, one 18-pin
and two 8-pin sockets
sockets_i6_07086x400
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!

ic_sockets_on_v2_3_boardx600
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.
11 TX TEST pushbutton, 4-pin
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.
tx_test_on_v2_3_boardx600

12 C9, C10 18 pf
C9_i6_07015scale
c9_soldering_i6_07127x340
ceramic disk
c9_on_v2_3_boardx600
⇐ When stuffing the capacitors, direct the wires so they don't cross. This will enable you to solder the pads without shorting.

13 C12, C13 22 pf
C12_i6_07020x190
c9_soldering_i6_07127x340
ceramic disk
c12_on_v2_3_boardx600
⇐ When stuffing the capacitors, direct the wires so they don't cross. This will enable you to solder the pads without shorting.

14 C7, C8 0.01 f 2.5%
C12_i6_07023
Red and yellow or grey; if grey marked 10 nF
c7_on_v2_3_boardx600

15 C3 100 pf
C3_i6_07026x190 ceramic disk 100pf
labelled 101
ceramic disk or dipped
c3_on_v2_3_boardx600

16 C1 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    C1_i6_07054
c1_on_v2_3_boardx600

17 RX TEST SPDT
rxtest_part_i6_07139x340
slide switch, 3-pin. Orientation doesn't matter.
rx_test_on_v2_3_boardx600

18 Q1 PN2222 transistor
q1_part_i6_07078x340
3-pin -- orientation is important! Line up part with silk-screen.
Do not confused with U1
q1_on_v2_3_boardx600

19 U1 Regulator MCP1700-3302E
or
MCP1700-3002E
u1_part_i6_07143x340
3 pin
Install so the flat side is toward the edge of the board.
u1_on_v2_3_boardx600

20 JP2 2 x 5 header
J2_header_part_i6_07048x340
jp2_part_i6_07152x340
Insert on top, solder from bottom
jp2_on_v2_3_boardx600
Short pin goes down through the board.
Long pin side is up.
See pic on left.

21 Power up and test voltage

voltage_test__v2_3_573x800 volts_i6_07092x600
22 D5 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.
23 D4 Red LED (PTT)
d4_red_led_part_i6_07044x340
Polarized -- make sure the square end
lines up with the silkscreen.
leds_on_v2_3__i6_07973

24 R6 and R7 10K trimmer potentiometers
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.
r6_r7_on_v2_3__i6_07979

25 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.
de9_on_v2_3_boardx600

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.
26 U2 CML MX-614 Modem
mx614_part_i6_07165x340
16 pin IC
u2_on_v2_3_boardx600
27 U3 PIC16F1847 microcontroller
pic_i6_07093x600
18 pin IC
u3_on_v2_3_boardx600
28 U4 MCP6023 Op Amp
mcp6023_part_i6_07168x340
8 pin IC
u4_on_v2_3_boardx600
29 U5 23K640 Memory
23k640_part_i6_07166x340
8 pin IC
u5_on_v2_3_boardx600

30 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. You're done assembling the TNC-Pi.
Configure TNC-PI
© Tadd Torborg, 2014↝2017 -- all rights reserved