4. First Power-Up of the PCB

I could find no instructions about testing, etc. so I continued with my guesswork...

There are a series of connectors on the board and as I find out how they work I'll update the following list:

• USB1 - This is of course a USB interface for a PC.  Before plugging into your PC, install the drivers that come with the rest of the documentation.  On my set the application was called CH341SER.EXE.
• P1 and P10 - Connectors to allow you to daisy-chain several PCBs together.  Sounds like fun...we should have a convention where everyone gets together with their cubes and tries it out!
• P2 - This is a TTL level UART serial interface
• P3 - (Looks like an I2C serial interface)
• P5 - 5 volt power, centre positive
• P6 and P7 - These are the two rows of connectors into which the pre-assembled module is inserted
• P8 - (This says it is connected to an ADC (analogue to digital converter) to it might be a way to connect music to the system - just a guess)
• P9 - (No idea)
• ISPI - (I guess this is an SPI serial interface)

WARNING!
Before connecting your board to power I advise you to check the board carefully to make sure there are no mistakes and ALSO make sure that there are no loose pieces of wire lying around that could short the board out.

Test 1
I decided to power up the board and see what happens when you don't have the LED cube attached (because we haven't built it yet).

Two modules come with the kit - one with a jumper on the two-pin header (I will call this Module A or 'Automatic' module) and one without a jumper (Module B or Serial Module).  I inserted Module A for this test.  I connected the power connector to a 5-volt power supply.  On my power supply I can specify the maximum current which I set at 200mA.

On power-up it the LEDs on the PCB are illuminated and the board consumes between 130/140 mA.  After a few seconds this rises to 170/180 mA.

I am fortunate enough to have an oscilloscope so I then looked at the signals I was getting on the 8 x 8 array of connectors which the cube will plug into.  Looking at the effects I was seeing on the screen of the oscilloscope it was obvious that I was seeing a waveform that represented the various patterns that one would expect to see if the cube was running.  I therefore assumed (correctly as it turned out) that 'Module A' is pre-programmed with a sequence of effects.

The fact that the cube electronics were running gave me the opportunity to go round and test all 64 of the pins in the 8 x 8 matrix to check that they well all working.  The waveform I was seeing on each pin continually varied depending on the pattern the microcontroller was trying to display but a typical display looked like this:

I went around and tested them all and - shock! - one of them wasn't working :-(  Pin 11 on U2 wasn't giving me any signal!  So I used my multimeter to check the continuity between the gold connector and the pin of the chip.  Sure enough, there was no connection.  Closer inspection showed I had a dry joint on the chips - oh well, not bad to have just one - so I got the soldering out again, turned the temperature back down to 310 degrees, applied some flux and re-soldered it.  A quick check afterwards showed it was now working okay! :-)

I appreciate that if you don't have an oscilloscope that this test is not going to be possible but it takes such a short time that if there's any way you can ask a techie friend to help you test the board I'd encourage you to do so - you don't want to assemble the whole cube and then find out there's a problem!

Test 2

The next test I did was to connect the board to my PC via the USB connector.  I first installed the drivers (as mentioned above) and the connected it up.  The USB connector supplies power to the board so you don't need to plug power in as well.

Plugging it in, the LEDs flash on briefly, then go off for a few seconds, and then come on.  That was it.  Not very exciting.

I then tried running the program called 3D8S_alpha.exe program.  The display looked like this...

 ...and you should be able to see that in the 'Communication' section the application appears to be set up to communicate via COM17.  I checked in the PC's 'Device Manager' and it said that this was called 'USB-SERIAL CH340'.  So it seems that the device driver I installed is working.  I then pressed 'Connect' and the LEDs went off for a couple of seconds and then on again so I assume something is working!  We just need to build the LED cube now and start to play with it.

(By the way, if you press 'Play' the display shows an animation of what each plane of the LED cube will be doing when it is running through a sequence - fascinating to watch!)

My conclusions were that Module A is for an 'Automated' pre-programmed display and Module B is for use with external control devices like a PC.

Let's now see how we get on with the construction of the cube...