HOME

 

how to find & fix most common mistakes

Troubleshooting

learning fault-finding

No panic

In this arteicle we will give you a detailed explaination of the techniques to use when your Nutchip circuit seems not to work.
Sometimes circuits don't work at the first attemps: it's normal, don't be worried about it. From time to time, you can end up with a damaged part, but contrary to popular belief, it is quite a rare event. The golden rule is: Electronics = Precision, therefore checking with great patience an perseverance all of the parts and connections in a circuit you will always be able to find why a circuit fails, and be able to fix it..

What do you need

The procedure detailed below applies to this configuration:

I need also:

pc interface
..
base circuit       


Base circuit setup

It is essential to check carefully the base circuit used to test and program the Nutchip. Assemble a circuit according to the schematic above, and use a a socket for the Nutchip. Do not fit the Nutchip in its socket now, as it is necessary to execute the following checks first:

- with the multimeter, check for the presence of 5 volts between the Nutchip's socket pin 20 and pin 10. Positive (red) lead of the multimeter goes to pin 20, negative (black) to pin 10.
- now put the positive (red) lead on socket pin 1 (keep the negative on pin 10)  and check that 5 volt is present
- check the ceramic resonator (OSC). Does it have three pins? This is the only kind whith embedded capacitors, see photo on the right. You can also use a quarts crystal or a two-pin resonator, but the you need to add two capacitors externally (see base connections for an example)
- with a short wire jumper, short briefly pins 10 and 19: if connected correctly, the LED will flash.

Do not put the Nutchip on the board if any of the above checks fails!

- check the resonator (or crystal) frequency, which is usually marked on its case. As you need a 4 MHz part, look for nubers like 4.00, 04.0, 4.0000 etc. A part with the wrong frequency will not damage the Nutchip, some will work as well (but with the chip running at different pace than intended) but will almost certainly impede state-table programming.

How to test a brand-new Nutchip

Nutchips are supplie pre-programmed as LED flashers. Therefore, when you insert them in the base circuit they will make the LED flash automatically.
A brand-new (i.e. not reprogrammed) Nutchip makes exactly 2.5 flashes per second (0.2 sec on, 0.2 sec off).

If the LED does not flash:
- check that the Nutchip is not reversed on its socket
- check that all pins are inserted correctly in the sockect holes, some pins could be inadvertently bent under the chip.
If the LED flashes:
- check the flash rate: you must count exactly 25 flashes every 10 seconds (150 flashes/min). If the rate differs, your resonator in out of frequency, replace it with a 4 MHz part.
 

PRE-LOADED FILE

A brand new Nutchip comes already loaded with the file "collaudo.nut". This truth table is not only capable to flash all outputs, it recognizes also four keys (key1 to key4) of the Visa Simplex infrared remote control (or the Nutchip Commander as well).

Pressing one of these keys stops the relevant output (out1=key1, out2=key2...) for 1 second.

This way you can test an infrared receiver (using the Visa Simplex remote) or the serial connection to the PC (using Commander)

 

Nutstation configuration

Be sure to have the latest software release (check the download page), and follow carefully the Nustation install instructions.
When running Nutstation for the first time, click on the setup icon to select the serial port to use for Nutchip programming.

Warning - sometimes the labels on a PC serial port do not match the actual COM port number as assigned by the computer operating system! Therefore the label can say a port is #1, while the operating system refers to the same port calling it the #2.
Later we will see how to check a serial port using the signal tracer.


setup

Check your serial cable

Check with the multimeter in the "ohms" or "buzzer" position for cable interruptions. The serial cable must be an extension cord, that is pin 1 in the male plug must connect to pin 1 on the female plug, pin 2 to pin 2, and so on.
Right after the check for cable breaks, it's time to check for short circuits between the pins.
Avoid using cables more than 150 long. When possible, connect the PC interface directly to the base circuit, keeping the wires connecting CN2 to CN3 as short as possible. But if you use a cable, then check it, wire by wire.

How to check for short circuits with a multimeter:
You need to check only the cable end with the female plug. With the first probe touch the pin 1, while touching all of the remaining pins - one after another - with the second probe. Then move the first probe from pin 1 to pin 2; with the second probe, touch the pins 3,4,5,6,7,8,9. If none fails, move the first probe from pin 2 to pin 3; and touch the pins 4,5,6,7,8,9. continue appling this technique until you have moved the first probe to pin 9. If you have found no short circuits on these pin pairs, there are short circuits at all in the cable.

Building a signal tracer

With this trick you will be able to follow the serial signal from the PC to the Nutchip and back, discovering hidden interruptions along the way. The trick works because the programming signal fall in the audible range, which makes it possible to listen it with an ordinary earphone.
The internal electrical resistance of ordinary (walkman type) earphones is too low for direct use, and we are going to place a 2200 ohms series resistor to increase it to an acceptable level (see photo). The resistor has the additional advantage to protect the earphone from DC voltages that could otherwise damage the earpieces.

The photo shows how to connect the resistor to the earphone, by means of a pair of cables with crocodile clamps. One end of the resistor is wrapped to the tip of the earphone plug. The yellow crocodile bytes the center ring of the plug. Ensure that the crocodile touches only the center ring and does not get in contact to any other plug contacts. To avoid unwanted short circuits, lock firmly the parts to the table top using adhesive tape.

The programming signal starts with a short bleep, followed by a series of regularly paced cracks. Normally, the serial signal departs from the PC serial port pin 3, and goes to the pin 2 on the Nutchip. Following the PC interrogation, the Nutchip sends back its responses from pin 3, directing them to the PC pin 2.

how to connect the earphone, the resistor and the two crocodile cables.

"Following" the signal: departure...

Start Nutstation and load the file "led_flasher.nut". Do not connect the interface or the Nutchip to the PC.

 1) START FROM PC


Spot the serial port connector on the PC. Connect the green crocodile cable to pin 3 and the yellow one to pin 5.
Warning: Be careful not to touch any other pin and not to make any short circuits.
Clicking on the "program Nutchip" button should cause a short bleep on the earphone.

If you don't ear any bleep:

- You are testing the wrong serial port. Configure Nutstation for using a different serial port, alternatively connect the signal tracer to anoter serial port and try again.

- The serial port is disabled or unavailable on your motherboard. Sometimes a serial port is disabled from the BIOS. Follow your motherboard instructions in order to activate the port again.

- The serial port is not working. Ask your PC dealer for replacing it or to buy an additional serial port.

- The serial port is locked by another application or by the operating system (e.g. used by the mouse or a modem). Reconfigure it or buy an additional serial port.

 2) CONTINUE WITH THE SERIAL CABLE


Connect the serial cable to the PC. Do not connect the end with the male 9-pin plug. Connect the green crocodile to pin 3 and the yellow one to pin 5. Clicking on the "program Nutchip" button you should hear a short bleep.

If you don't ear any bleep:

-  The cable is defective. Check it or replace it.

 3) TEST THE INTERFACE


Connect to the cable the interface and the base circuit, but without the Nutchip (extract it from its socket). Power the circuit from a stabilized 5V DC supply.
Connect the yellow crocodile to +5V and the green crocodile to the pin 3 on CN2 (RX).
Clicking on the "program Nutchip" button you should hear a short bleep.

If you don't ear any bleep:

The interface is not working. Connect the green crocodile to the pin 3 on CN1 (TD), in order to check the connector. Check resistor colors: do they match the expected part values? Is pin 5 on CN1 connected? Do the part transistor part number match the schematic or are they swapped? Are there any short circuit (check with a lens)? Is CN2 reversed? Is the +5V present between pin 4 and pin 1 on the connector CN2?

         

   RESISTOR COLORS
  
R1, R3=4700 YELLOW/VIOLET/RED
   R2, R4=10.000 BROWN/BLACK/ORANGE  


 4) EXAMINING THE BASE CIRCUIT


If no failures found yet, it's time to start examining the base circuit (which is still missing the Nutchip). Using thin bare copper wire to touch the Nutchip socket pins, connect the yellow crocodile to the pin 20 and the green one to pin 2.
Clicking on the "program Nutchip" button you should hear a short bleep.

If you don't ear any bleep:

-  there is connection between CN2 and CN3, or one of them is reversed
- check the connection between CN3 and the Nutchip socket: please note the numbering, the connector pin 3 goes to the Nutchip pin 2.
- use the multimeter to check against short circuits between socket pin 2 and 3, 3 and 4, 1 and 2 (remove power to perform this check). 
.

 5) FIT THE NUTCHIP


Remove power in before placing the Nutchip into its socket. Be careful not to reverse it, pin 1 is marked by an engraved dot on the chip case.
Connect the yellow crocodile to the +5V and power the circuit. With the green crocodile touch the Nutchip pin 2 (in order to prevent short circuit, instead of the crocodile tip you can touch the pins with a needle or thin copper wire connected to the crocodile).
Clicking on the "program Nutchip" button you should hear a short bleep.

If you don't ear any bleep:

- the socket is not soldered correclty. Check solder joints.
- the socket does not connect correctly to chip pins, or the chip is not completely inserted in the socket
- one or more pins are not inserted in the socket (sometimes a pin is bent under the chip body)
-  the Nutchip is reversed (rotated half turn)

... and retour

CONGRATULATIONS, you are halfway in our signal journey. If you successfully followed all of the steps, your PC is now correctly configured and the Nutchip receives the programming signal.

Let's continue using our simple signal tracer to following the response signals that the Nutchip sends back to the PC.

    
SIGNAL JOURNEY PC-NUTCHIP-PC
DEPARTURE
   
RETOUR
Pin 3 on CN1 - R2 - Q1 base - Q1 collector - Pin 3 on CN2 - Pin 3 on CN3 - Nutchip Pin 2   Nutchip Pin 3  - Pin 2 on CN3 - Pin 2 on CN2 - R4 - Q2 base - Q2 collector - Pin 2 on CN1

 6) NUTCHIP ANSWERS START FROM PIN 3


Connect the yellow crocodile to GND (negative supply lead). With the green crocodile touch the Nutchip pin 3 (in order to prevent short circuit, instead of the crocodile tip you can touch the pins with a needle or thin copper wire connected to the crocodile).

Clicking on the "program Nutchip" button you should hear a rithmic cracking sound.

If you don't ear any rithmic sound:

- pin 3 is bent under the chip body
- the ceramic resonator or cristal has the wrong frequency (you must use only 4 MHz parts)
- with the multimeter, check for the presence of 5V DC between Nutchip pin 1 (RESET) and 10 (GND)
- defective solder joints, especially on pin 3
- the socket does not connect correctly or the chip is incorrectly inserted in the socket
- the three-pin ceramic resonator is defective or not soldered correctly

 7) INTERFACE, PART 2: FROM NUTCHIP TO PC


Keeping the yellow lead connected to GND, connect the green crocodile to the pin 2 of CN2 (it could be easier to connect to the R4 lead which connects to CN2).
Clicking on the "program Nutchip" button you should hear a rithmic cracking sound.

If you don't ear any rithmic sound:

- there is no connection between CN2 and CN3
- check the connections between CN3 and the socket: note that the connector's pin 2 goes to Nutchip pin 3
  

 8) BACK TO THE PC


Keeping the yellow lead connected to GND, connect the green crocodile to the pin 2 of CN1 (RD).
Clicking on the "program Nutchip" button you should hear a rithmic cracking sound.

If you don't ear any rithmic sound:

-  check that Q2 is not reversed. With the multimeter in VOLT position, check for +5V between the emettitor (red lead) and GND (black lead).
-  check again the connections of Q2, R3, R4. Is the Q2 part number correct? If you use an equivalent, check the datasheet for any difference in the pinout and verify that it is actually a PNP signal transistor.   

 9) LAST SECTION OF THE CABLE


If all of the above test secceded, the last part to be checked is the return wire on the serial cable. One should touch the pin 3 and 5 of the female plug while it is functioning. This is an impossible measure with commercial cables, whose plugs cannot be opened. Therefore, if your Nutchip still fails programming:

- the serial cable is defective, replace it
- the PC serial port is broken, use another serial port or buy an additional serial port
- there is an hardware conflict on you motherboard. As an example, an internal modem board, if not correctly configured, can interfere with the serial port. Older audio cards can intercept or cause false COM interrupts. If possible, remove the boards and/or disable them from the system.
- there is a software conflict. The serial port is shared with other accessories? As an example, some digital camera or cell phone drivers poll periodically the serial ports to see if a device is connected. Such an interference interrupts the Nutchip programming. Remove or disable any driver or software that uses the serial ports.

Additional tips...