Testing
Now you've finished soldering FIGnition you'll need to test it. It's tempting just to power it on, but if you've made a mistake, then you could find you'll have wasted an hour or more of work and / or the money you've spent on the kit!
So, testing is possibly the most important aspect of engineering, of building FIGnition. To test safely we first test with FIGnition powered off and without any chips inserted; then we make some powered tests and finally connect everything and run it! The testing phase involves using a Multimeter.
Visual Testing
Turn the PCB upside down and carefully check all the joints. Make sure all your connections look good. Good connections tend to look nicely cone shaped. I never accept a connection that has gaping craters in the pin/pad connection or doesn’t appear to smoothly connect to the pin. If you see a potential problem, remember it’s easy to retouch the solder joint, and add a tiny amount of solder if there isn’t enough.
Check that you haven't accidentally bridged connections that are close to each other. You can fix this by cleaning the tip of the iron first to remove excess solder and then remelting those connections. Usually they will re-separate with a little patience.
Look for what’s called ‘solder splashes’: random bits of solder splashed across the PCB, they may cause inexplicable problems when they become dislodged and randomly connect pins together. You can flick these off with a small flat-headed screwdriver.
Make sure you’ve snipped all the legs from your components to no more than 1 or 2 mm (mine are generally 2mm) from the PCB.
Finally, check to see that all the components are in the right places and (with the exception of resistors) have the right orientations. If You’ve Made a Terrible Mistake and you find some components will have to be removed, you'll need the solder sucker; I’ve provided a link to how to use one.
Unpowered Tests.
Before powering up the circuit we should check the connections using a multimeter. It’s quite exhaustive. The connections correspond to the PCB layout below (FIGnition FUZE):
This is how I number pins on the PCB:
All the simple 2-pin components are numbered with pin 1 on the left (if they’re going horizontally) or pin 1 at the top (if they’re vertical). Each Phono pin 1 is the one at the right and pin 2 is in the middle.
Switch pins are numbered according to the above orientation: pin 1 is top, left; pin 2 is bottom left; pin 3 is bottom right, pin 4 is top, right.
IC pins are numbered according to standard chip pin numbering: pin 1 is top left, then below is pin 2 and so on until we get to the bottom of the IC; then the pins are numbered from the bottom, right on the chip going up to the top right pin. So, pin 1 of IC1 is top left, pin 14 is bottom left, pin 15 is bottom right, pin 28 is top, right.
The USB is ordered differently: Pin1=Bottom left, pin 2= bottom right, pin 3 = top right, pin 4 = top left.
Checking Shorts
The most important thing is to check for shorts . It's easy to accidentally connect two pins that SHOULD NOT be connected and this can result in damaged components, due to current overloads on pins.
First check is that VCC and GND aren’t shorted, by touching one multimeter probe on C1.1 and the other on C1.2 (the big capacitor). You might hear a click, but you should not hear a tone from the Multimeter.
Next check connections that are next to each other aren't shorted.
Check U1’s vertically adjacent connections (i.e. U1.1 shouldn’t connect to U1.2. U1.2 shouldn’t connect to U1.3 etc). No adjacent connections should connect.
Check U2’s vertically adjacent connections. Only U2.7 and U2.8 should connect.
Check U3’s vertically adjacent connections. Only U3.7 and U3.8 should connect.
Check the USB signal connections. No adjacent connections should connect.
Check C1, C2, C3, C4 and C5. Pins 1 and 2 should not connect to each other. You may hear a very brief click as the capacitors discharge, but that's OK.
With switches, the horizontal connections on a particular switch should connect, but SW1.4 and SW2.1 shouldn’t connect as shouldn’t SW2.4 and SW3.1; SW3.4 and SW4.1. Similarly, SW5.4 and SW6.1 shouldn’t connect, SW6.4 and SW7.1 shouldn’t connect. SW7.4 and SW8.1 shouldn’t connect. SW1.2 shouldn’t connect to SW5.1; SW2.2 shouldn’t connect to SW6.1. SW3.2 shouldn’t connect to SW7.1 and SW4.2 shouldn’t connect to SW8.1.
LED.1 and LED.2 shouldn’t connect.
Checking Connections
After checking what shouldn't be connected. We can should check what should be connected. Each cell in the table below lists up to three pins that should all connect. Set one probe of the multimeter on the first pin in the list and the other probe on the second pin in the list. The Multimeter should sound a clear tone. Then set the second probe on the third pin in the list (if there is one), but don't move the first probe: the multimeter should make the same tone again. For example, the first cell says "U1.1, VCC, USB.1" . That means you connect one probe to U1.1 and the other to a VCC connection and the multimeter should sound. Then you move the second probe to USB.1 and the multimeter should sound again. Then you go to the next cell; connect the first probe to U1.2 and the second to PD01.1: the multimeter should sound. There's no third pin so you move to the next cell ("U1.3, D1.2, PD01.2") and test those connections etc until you get to the end of the table. Mark each test as you complete it (so you don't do them twice!)
Powered Tests
You’re now ready to start testing the board with actual power connected, but we still won't insert the chips yet: instead we just want to test the board can be powered.
Again, check there’s no stray bits of metal under the PCB, nor stuck to the underside of the PCB!
Make sure the USB-B cable is NOT plugged into a USB power adapter.
Next check the USB-B cable can plug into the USB-B socket. Hold only the edges of the PCB and insert the USB-B cable, then remove it.
Connect your USB cable to your USB power adapter.
Whilst touching only the edge of the PCB and (and getting ready to remove it if there’s a problem) insert the USB-B connector.
If there’s no smoke or pops or anything else, then you’ve passed the first power-on test!!! Well done!!!
Part Two: Power On With Inserted Chips.
Now REMOVE the USB-B lead from the FIGnition computer!!!
Inserting The ICs
For some reason manufacturers supply ICs with their pins splayed out, but the sockets need them to be vertical as shown below:
You’ll need to bend them all at the same time so they stay in line, but they’re fairly fragile, so you need to be careful. Start with the 8-pin ICs as they’re easier.
Hold a chip with one end in a pair of pliars and the other end between your fingers.
Then level the pins against a straight wooden surface for one side.
Then carefully lever the body of chip until it's just past vertical (being careful not to touch the pins themselves with your fingers)
Repeat the process for the other side.
Repeat steps 1 to 4 for the other 2 chips - NOTE: The legs on the U1 chip may look straight, but it might not be enough to fit in the socket. In that case you should use this process to bend them a little more.
Now you’re ready to insert the chips.
Start with U2 (which says “23K640” or "23K256" on it) then U3 (which says “AMIC” on it) then U1 (the big chip). Inserting the chips is a bit of a procedure in itself:
Place the PCB on your bench with the front side of the PCB facing you.
Locate the notch on one end of the chip. That’s the end that should point to the top of the PCB (towards the USB and Phono sockets).
Use your fingers to hold the chip by its plastic body, at the far ends of its body, whilst avoiding touching the legs as they can be damaged with static electricity.
Carefully insert the chip into its socket WITHOUT bending any of the legs, or twisting them etc. You might need to readjust the legs (using pliers of course), but you must make sure they’re all located well enough before applying force. You’ll need a certain amount of force, but it shouldn’t be too hard just using your fingers. Remember to insert the chips with even force since if one side or end goes in first it may twist or bend the legs of the other end, preventing it from fitting.
Again you need to do some checking.
Check the pins have all gone in OK (there’s no metal pins squiffing out of a socket).
Check that the notch on each IC is pointing to the top, which is towards the USB and phono sockets (otherwise you’re likely to burn out entire chips as you’ll connect VCC to its GND pin and vice-versa).
Check that U3, the one on the right says “AMIC” and that U2 the one in the middle says “23K640” (or "23K256") on it.
Once you’ve done that you’re ready for the next test:
Whilst touching only the edge of the PCB and (whilst getting ready to remove it if there’s a problem) insert the USB-B connector.
If there’s no smoke or pops or anything else, then you’ve passed the SECOND power-on test!!! Well done!!!
Wait a little while to see that it continues to be OK. The LED shouldn’t light and nothing else should happen for the moment.
OK, remove the USB-B connector again.
Now let’s try it with your TV. CRT TVs work best, and most LCD TVs will work.
Plug one end of your phono lead into your TV.
Turn on the TV.
Select the correct video input (I guess either SCART or Composite depending on how your phono lead connects to your TV). With the correct connection the image should be a steady black image even before you’ve powered on the FIGnition computer.
Plug the USB-B connector back in without touching any of the keys on the keypad. The FIGnition logo should instantly appear and a couple of seconds later the Copyright message will replace it and FIGnition is ready to be used:
CONGRATULATIONS - YOU’VE BUILT YOUR OWN COMPUTER FROM SCRATCH AND IT STARTS UP!!!! Now it's time to blog, tweet or Facebook about what you've Done :-) !
Next, if you have a FIGnition inFUZE from RS Components, head off to the Keypad guide on the leaflet and see what you can type (this also tests the keypad!).