|These are the assembly instructions for the N9600A4r2 blue-board. Make sure the silkscreen information on the board you are assembling matches this. The bill of materials linked below is specific to the N9600A4r2 board.|
|Bill Of Materials||
Right-click on this link and save the n9600a4 bom csv file to your computer.
This is the Digikey shopping list for the NinoTNC.
Find the n9600a4 csv file on your computer (it will be named starting with n9600a4 and will be a csv, comma separated values, file)
|Go to Digikey website||Click on this link: Digikey|
|Shopping Cart||Click on the shopping cart. If presented, click on View Cart button.|
if there is no New Cart button, skip to Upload CSV,
else click the New Cart button.
There is an Upload A File field in the middle of the form.
Drag the CSV file from your Finder/Explorer into that field,
or click on the Browse link,
and then navigate to the CSV file.
You will see a pop-up window titled "Upload File Mapping".
Find the titles (in row 1) on that window and make sure the column headers match the text in the title row.
Make sure the third column ROW drop-down says "Customer Reference".
Tell it to start the First Part-record on line 2 (not the titles on line 1).
Click on Add To New Cart
If you need a USB A male to USB B male cable, add it now.
Part# WM21039-ND is $2.16 for a 3'4" cable. There are suppliers of 1 foot USB-B cables at other vendors (Amazon).
Short is better for RF immunity but it does have to make it from the host computer (Raspberry Pi) to the NinoTNC.
Inspect the list. If anything is backordered, stop and send an email to firstname.lastname@example.org email reflector.
Almost everything is available from a second source right on Digikey. We'll fix it and send a reply.
If you go ahead and let it be backorded, DigiKey will charge you postage twice.
Now do checkout and pay for your order.
Shipping: USPS shipping is the cheapest.
|⇒ All parts are inserted from the silk-screened side of the board, i.e. from the side on which the white writing is printed.|
|⇒ Except where specifically noted, all two pin components are non-polorized so you can put the part onto the board with the pins in either hole.|
|1||Y1||7.3728 MHz crystal
||The crystal will have some lettering on it containing the numbers 7.37
The crystal and two capacitors, C4 and C5, form an oscillator to provide clocking for the CPU's digital circuits.
|2||R4, R15, R16, R17||100 k Ω 5% 1/4 W resistor
||R4 is part of the output impedance/level control, along with RV1 - TX Deviation Adjust. R4 is bypassed by the Mic/Data DIP switch.
R4 attenuates the TXA signal to support low-volt, high sensitivity microphone inputs to use NinoTNC
R15, R16 and R17 are a filter in the receive circuit.
|Note: the color codes on the 1% resistors are pretty hard to use. If you are receiving your resistors in a mixed bag of parts, you probably want to do all of the remaining resistor steps before soldering the resistors so you can double check the color codes before you solder and cut. I recommend using a VOM to prove that each 1% resistor is what you think it is, and not one of the other values.|
|3||R10||7.87 kΩ 1% 1/4 W resistor
||This resistor is in the input and feedback loop for the 2nd op-amp stage in the TX-data/audio path.
|4||R11||47 kΩ 5% 1/4 W or 1/8 W resistor
1/8 W shown
|R11 turns off the MCLR input to the CPU in the normal case when a PIC-Kit programmer tool is not attached to the ICSP connector (J4).
The PIC-Kit uses this input to reset the CPU as needed when programming or debugging.
If this resistor is missing, the MCLR line would float across many voltage levels, causing intermittent CPU resets.
|5||R12||4.75 kΩ 1% 1/4 W resistor
||This resistor is in the audio path between the 1st and 2nd op-amp stage in the TX-data/audio path.
|6||R13||7.15 kΩ 1% 1/4 W resistor
||This resistor is in the input and feedback loop for the 1st op-amp stage in the TX-data/audio path.
|7||R14||14.7 kΩ 1% 1/4 W resistor
||This is part of the filter circuit for the 1st op-amp stage in the transmit data circuit.
|8||R18||15 kΩ 5% 1/4 W resistor
||R18 is part of the amplification circuit for the Receive audio op-amp.
|9||R19||150 kΩ 5% 1/4 W resistor
||R19 is part of the amplification circuit for the Receive audio op-amp.
One of the SIGNALS switches, 1x/11x, bypasses this resistor.
If this resistor is bypassed by the switch in the UP (toward edge of the PCB) position, then the gain of the amp is 11x.
If this resistor is in circuit, switch in the DOWN (toward the TARPN logo) position, then the gain of the amp is 1x, which is also unity gain.
|10||C4 and C5||18 pF 5% 50 V Ceramic capacitor (may be 100 V)
marked 18 with a following letter.
|C4 and C5 are part of the crystal oscillator circuit
|11||C8, C12, C13||0.1 µF 10% 50 V Ceramic capacitor
||These ceramic radial capacitors provide power supply filtering and glitch reduction on the CPU’s main power input and two other places on the board.
|Be careful here. Starting now we'll be installing components which are polarized. That means you have to get each pin in the correct hole.|
|12||Q1||MOSFET 100v 1.3amp 4-pin DIP PTT driver.
Metal Oxide Semiconductor
|Install so the two shorted-leads (see images) are away from the TARPN Logo.
The two independent leads are nearest the Q1 symbol.
You'll have to squeeze the pins across the chip so they line up with the holes.
You can test insert on the bottom of the board where there are no part-neighbors.
Once you have the chip inserted in from the top of the board, go back to the bottom of the board and spread two corner pins out so the part is heald in place. See images. This four-pin device is driven by a GPIO on the CPU and is responsible for pulling the PTT line to ground when the NinoTNC wants to send a packet. The device takes a turn-on signal, in the form of very little current at 3.3v, from the CPU. If no turn-on current is present, the output of the MOSTFET is allowed to float. The radio will provide a pull-up voltage. When used with a microphone, the measured voltage on the PTT wire is whatever the radio generates. When the microphone button is squeezed, the PTT wire is grounded to the radio ground, bringing the voltage to a relative 0 V. When used with NinoTNC A4, the PTT wire is fed into, or out of, the TNC through the DE9 connector, directly to the MOSFET pins 3 and 4. If the CPU is not asserting its turn-on signal to pin 1 of the MOSFET, pins 3 and 4 are dragged up by the radio's PTT voltage. When the CPU asserts 3.3 volts onto its GPIO output, wired directly to pin 1 of the MOSFET, the MOSFET shorts pin 3 and 4 through its internal diode to pin 2, which is ground on the NinoTNC and ground on the DE9 connector. When the CPU is asserting the PTT as active, the 3.3v also drives LED D1 to turn on. Note that the LED can function even if the MOSFET is completely missing, so D1 illuminating is not a sign that the MOSFET is installed correctly or working. We chose this MOSFET to replace the opto-isolator because the opto-isolator couldn't drive PTT low enough to key up some older Icom radios. Those radios needed the PTT switch to be more like a button than a transistor. The MOSFET does a good job.
The other design consideration is that we want to prevent leakage between the PTT wire from the radio into the CPU. With the TNC we started with, the TNC-PI, it was possible for the CPU to power itself from the leakage through the NPN transistor. This is still an uncertainty because, though we saw the CPU do some bad things, we never proved it was powering from the PTT leakage.
We went with the Opto-isolator, and then the MOSFET, instead of the NPN transistor, just to be sure.
|13||XU3||28 pin DIP IC socket for U3
||This is the socket for the CPU.
|14||U2||MCP1702 3.3 V 250 mA
TO92 case regulator
|This part takes the 5 V DC from the USB connector and regulates it down to 3.3 V, as needed by the CPU.
Align flat edge with the board silkscreen
Here is the schematic showing the regulator and its two caps. I talk about this circuit fragment again in the step where you add the two capacitors.
|15||RN3||5 resistor 180 Ω resistor network
||Orientation is important!
Pin 1 is identified by the square around the hole on the PCB and an interesting symbol near the end pin on the component. See schematic symbol below.
I had good luck by folding two of the leads in opposite directions to hold the part in place before soldering. Once you fold the two pins, align the part upright, then solder.
This five-resistor network provides an in circuit resistance to limit the LED current for each of the 5 LEDs
|16||C17, C18||1 µF
[metal] film capacitor
|C17 is part of a receiver filter between the DE9 and the CPU.
C18 is capacitive coupling just before the DE9 on the TXA circuit. C18 is bypassed by SIGNAL switch SW3. Capacitive coupling has the effect of moving AC (audio) waveforms such that they are relative to the recipient's own neutral. The input to C18, in NinoTNC's TXA output circuit, is alternating current audio wich is relative to the final op-amp's output. In this case the output is all elevated by 1.65 volts, so the negative going side of a sine wave could be just barely above 0 volts, where the positive going side is nearly at 3.3v. This 1.65 volts is called a DC offset. If DC/AC switch is off, i.e. AC, the TXA output goes through C18 and the DC offset is removed from the signal. Having the DC/AC switch set to off is the prefered mode of operation of the NinoTNC, at least at this time.
|17||C2, C3, C11, C15||10 µF 10% 16 V
tantalum dipped capacitor
|Carefully observe values and polarities.
Positive side is marked with a very small plus sign on the part, or a red stripe, and goes into the square solder pad/hole on the PCB.
The silk-screen actually + sign.
C2 is 5v filter on the input to the regulator.
C3 is the 3.3v filter on the output from the regulator.
C11 is vcap input to the CPU on one side and ground on the other. VCAP is a pin on the Microchip CPU used for an internal filter. I'm guessing it is to make the Analog to Digital converter input more stable.
C15 is part of a receive filter circuit, along with C1 R15 R15 R17, between the DE9 and the first receive op-amp stage.
C2 and C3
Click to zoom. The above image shows the positive + stripe on the capacitor lining up with the + on the PCB for C2 and C3.
As an aside, you can critique the soldering on this board. Notice how both sides of C2 and the + of C3 are well soldered and the - side of C3 isn't? The solder should be heated for long enough for it to flow through along the pin to show on the top side of the board. This is a technique that is really hard to be perfect at, but it's worth noting. Perfect soldering leads to the light side of the board.
C11 and C15
The above images show the positive + stripe on the capacitor lining up with the + on the PCB for C11 and C15.
better image of c15. Again with the soldering
|18||RV1 and RV2||10 kΩ 1/2 W cermet 1-turn side adjusted trimmer potentiometers.
10 * 10**3 = 10000 Ω.
Notice the arrow on one of the legs of the yellow cross. It is pointing down in this image.
|Place the two parts side by side in the appropriate holes. The yellow screwdriver adjustable end faces the edge of the board.
Solder one pin on each part.
Hold each part with a finger while heating the one pin so the solder melts and the part can be pressed flat to the board.
Let the solder harden, and then solder the other two pins.
Finally, go back and wet the original pin and let the solder reflow around the pin.
RV1 adjusts the Tx Audio level at the output of the TXA op-amp pair.
RV2 adjusts an input to the CPU and is used by the program to set the transmit preample duration. This preamble compensates for the time needed for the transceiver to switch from receive to transmit.
[metal] film capacitor
|This is part of the feedback loop in the 2nd stage of the transmit data output.
[metal] film capacitor
|This is part of the feedback loop in the 1st stage of the transmit data output.
|21||C7, C10||1200 pF 50v capacitor
or blue ceramic
|In the transmit Op Amp chain, these two capacitors are across the input on each of the first two stages.
|There is one capacitor left over, marked 15J100 0.15uF. . We'll use it in one of the last steps.|
||This socket has 6 solder points, two of which look like they'll get in the way when you insert them. They don't.
But they will hold this connector onto the PCB.
Solder all 4 pins and the 2 support items.
|23||SW1 and SW3||4 position dip-switch
||Install each switch so the label 1 2 3 4 is toward the TARPN label edge of the board.
Each switch is a separate circuit. SW1's four switches pull four separate CPU inputs on the CPU to VCC, and are used to select options. SW2 has four different circuits... more coming. One switch bypasses a resistor which, if the switch is off, reduces the output drive level such that a microphone input radio can be used.
|24||SW2||side facing push button switch labelled TEST TX
Mount so switch button faces off the edge of the board, directly away from the J3-pins in step 24.
Solder one of the smaller pins (not the switch shell), then, while pressing the switch into the board, wet the pin's solder again and make sure the switch is fully flush to the board.
This switch will tell the NinoTNC to send a transmit-audio-calibration tone and also generate a transmit packet from the saved callsign and to "CQ". The transmit packet is held until the switch is released.
While the switch is held the NinoTNC will send one of 4 calibration tones which can be used for setting TX-LEV.
On release, the NinoTNC sends a KISS frame back to the host with diagnostic data, and the NinoTNC also transmits the queued packet.
Electrically, pressing this button connects a GPIO input on the CPU to VCC.
Releasing lets the GPIO input be pulled to ground by the CPU's internal configurable "weak pulldown".
|In the next steps you'll be soldering 5 LEDs onto the PCB. When you cut the leads, save the trimmings for use as scope test loop wire in a later step. You only need 3 longish thick wire leads for the scope test loops, but save as many as you can for practice purposes.|
|25||D1, D3, D4, D5, D6||LED installation
In this step you are going to bend the leads of all 5 LEDs.
What we need is a fixture to allow all 5 LEDs to be bent the same so they point out the end of the board. It is only critical that the LEDs be perfect lengths and all the same direction if you intend to ever show this NinoTNC to anybody. It's even more critical if you obtain a housing for the NinoTNC made with the LED positions in mind. The leads need to be just long enough before the bend such that the LED lays over the end of the board and just misses the end of the board. We're going to use a USB connector for a guide. It happens to be exactly the correct size. Grab a USB A connector, just like the kind on a keyboard or mouse cable where it plugs into the Raspberry Pi.
Put the LED so the short lead is toward the cable side of the connector and the long lead is toward the plug.
The LED body's base will be against the wide side of the plug and the wires lay around the short side of the plug.
Now fold the wires over the wide side of the plug making a 90 degree bend.
Here is the result we want:
||TX - This LED is illuminated when the NinoTNC is keying the radio through the opto-isolator.|
||Data Carrier Detect. This LED will illuminate during radio received when several zero crossings occur in the wave-form (noise) which match the selected bit rate.|
||Last RX packet was decoded properly. This LED remains illuminated until a short time expires, or a packet is not decoded properly.|
||TX message is queued. The Pending LED illuminates when the NinoTNC has a message ready to transmit but hasn't had the opportunity to get rid of it yet.|
|D5||Red LED||CRC error on receive packet, This LED illuminates when a valid callsign field is received but the checksum/CRC on the packet doesn't match the rest of the packet and error correction either couldn't be applied, or didn't fix the problem.|
|26||U3||Microchip dsPIC33EP256GP502 CPU
||To make the chip fit into the socket easily, place the leads on one side against a hard flat surface and push on the package to bend the leads.
Then turn the IC over and do the same thing on the other side.
The pins themselves should be straight, but not splayed out like they are when the IC shipped.
Make sure the half moon on the IC matches the half moon on the socket and on the PCB.
As you insert the chip for the first time, don't push it all the way in.
Get all of the leads to go into the 28 holes, then reverse and pull the chip back out. It may be advisable to use a screw driver to gently lift one end a little, then the other.
Once the chip is removed, inspect the leads and make sure none of the bent while inserting. Fix any needing fixing and then insert the chip again, paying attention to the half-moon end as per the photo. If all goes well, push it in all the way.
|27||Test points GND, TXA, RXA||These are loops of scrap wire bent around the blade of a long-nose-plier.
||Test points for receive audio, transmit audio and ground.
Uses these to connect a high-impedance input audio amp to listen to packets, receive or transmit.
Or connect an oscilloscope to observe the receive voltage or wave form quality.
See pix below for installation.
|The integrated circuits installed in the next two steps are exactly the same size. They are of completely different function and if you put the wrong one in, thinking you only have one to go, you will have quite a bit of work removing it! Be careful that you grab the correct chip for this next step!|
|28||U1||MCP6004 quad op-amp
||Install the MCP6004 quad op-amp Integrated Circuit without a socket.
The pins will have to be bent a little to fit. See step 30.
Since the PCB is now rather crowded, and since the pin bending requirements and limits have no calibration, I recommend test-fitting the IC on the back of the PCB, and then when you get the pins bent as needed, move around to the front of the PCB and insert the op-amp where it needs to be.
This is a quad-package op-amp (operational amplifier) used to buffer the receive AF data signal from the radio and to condition and buffer the transmit AF data signal to the radio.
The quad op-amp has 4 separate amplifier sections. 2 of these are used in the transmit AF signal processing. 1 in the receive.
Make sure the half-moon shaped end lines up with the PCB as shown in the photos.
|29||U4||MCP2221 or MCP2221A
USB interface chip
|Install the MCP2221A USB-serial interface Integrated Circuit without a socket.
Make sure the half-moon shaped end aims toward the USB-B socket.
Note the extra header pins, J5, underneath where U4 MCP2221 is installed. These pins are for an optional header to be used if the NinoTNC will have a TTL interface and separate 5v source. This could be handy for an embedded project where USB interconnect would be inefficient. If you intend to use a TTL interface to the NinoTNC, don't install U4.
|30||C16||CAP FILM 0.15UF 5% 100VDC
||This capacitor is in the receive audio and serves to remove DC offset from the receive input.
If this part is missing, there won't be any receive audio.
See schematic below.
||This connector is the interface to the transceiver from the NinoTNC.
PTT, TXA data, RXA data, and ground are connected to pins 1, 5, 3 and 6 respectively.
Solder a center pin first, then squeeze the connector into the board and then reheat the center pin.
Now solder the remaining 8 pins and then the two outer fingers in 3 places each.
macmini:tadd$ ls -lrats /dev/*usbmodem* 0 crw-rw-rw- 1 root wheel 13, 0 Jun 13 10:30 /dev/tty.usbmodem14601 0 crw-rw-rw- 1 root wheel 13, 1 Jun 13 10:30 /dev/cu.usbmodem14601 macmini:tadd$
pi@raspberrypi:~ $ ls -lrats /dev/ttyACM* 0 crw-rw---- 1 root dialout 166, 0 Jun 13 10:58 /dev/ttyACM0