90 Silicon chip Australia’s electronics magazine siliconchip.com.auScreen01: the initial
splash screen, which is
quickly followed by...Screen02: a second
splash screen, giving the
software version and
build date, which is then
followed by...Screen03: the default
screen, which gives
volume control and
starts at 0dB. Rotate the
encoder knob to...Screen04: adjust the
volume. If can go up as
high as +12dB or down as
low as...
Screen05: -104dB.
Pressing either
pushbutton (or the knob)
on this screen takes you
to...Screen06: the main menu,
which has four options.
Use the rotary encoder
to change the current
selection and press S2 or
the knob to go into that
sub-menu.
Screen07: in the
crossover sub-menu, first
you select which band
you want to adjust using
the rotary encoder (you
can still adjust other
bands after making the
initial selection).Screen08: here we’ve
selected Band 2. Only two
bands are initially
available. You need to
change other settings
to activate Bands 3 & 4.
Selecting a band takes
you to...
next to the mounting hole in the lower-right corner of the
PCB) and connect the other end to the small LCD adaptor,
which you will have already soldered to the back of the
screen. Pin 1 is marked on that PCB.
If you don’t have that adaptor, you can separate the wires
in the ribbon cable and solder them to the 20 pins on the
LCD screen module, with the red wire to pin 1 and so on.
That’s how the original prototype was built, but it’s a tedi-
ous process, hence the adaptor board.
You can now apply power and check that the LCD screen
lights up and you get a sensible display on the screen. You
will need to adjust contrast trimpot VR1 before you see
anything on the screen. Also check that LK2 is in the VEE
position. Turn the rotary encoder and check that you can
scroll through the menus, and that pressing the front panel
buttons gives the expected results.
A lack of display on the screen could be due to several
problems. If you programmed the microcontroller yourself,
you know that it is at least running, but there could be a
soldering fault on one of the pins connecting to the LCD,
or there could be a wiring problem with the cable.
LED2 on the CPU board should flicker when the display
is updated, and you can force this to happen by turning
the rotary encoder knob.
As the CPU board has two onboard regulators and gen-
erates its own 3.3V rail, if it doesn’t work straight away,
then it’s a good idea to check that first. The left-hand pin
of CON5, labelled GND on the PCB, makes a good refer-
ence point. There is a via between CON5 (near the GND
terminal) and CON10 which connects to the +5V rail from
the power supply, so check this voltage first.
Next, check the voltage on the other terminal of CON5.
You should get a slightly lower reading, of around 4.7-4.8V,
due to the forward voltage drop of D15. Next, to check the
3.3V rail, probe either of the vias immediately to the left
of the PIC, IC11. The easiest one to reach is the one just to
the right of the capacitors to the right of JP5.
Expect a reading of 3.17-3.58V. Anything outside this range
suggests a problem with regulator REG2 or one of its associ-
ated components. Switch off and check the board carefully.
If the power supply rails check out, it’s a good idea to
verify that the primary oscillator is running. You will need
a frequency meter which goes up to at least 8MHz; some
DMMs have this function. Using the same ground point as
a reference, probe the left-hand end of the 470Ω resistor
near the bottom right-hand corner of IC11. You should get
a reading close to 8MHz.
If you don’t, then either IC11’s oscillator amplifier is not
operating (suggesting a problem with the chip, its soldering
or its programming) or there is a problem with crystal X2.
If you are seeing the 8MHz signal but still not getting any-
thing on the LCD, that suggests a connection problem between
the chip and the LCD, so check all the headers and cables.
If LED2 is not flickering, IC11 may not be programmed cor-
rectly or there is a bad connection somewhere, probably
on the CPU board.
It’s also possible that LED2 has been installed backwards.
If you’ve verified its orientation and the chip programming,
and it still isn’t lighting up, check your soldering carefully.Plugging the rest of the boards in
Assuming you have had success with the LCD and con-
trols, you can now connect the other three boards. As