106 Silicon chip Australia’s electronics magazine siliconchip.com.au
ASK SILICON CHIP
Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line
and we’ll answer your question. Send your email to [email protected]Tricky fix for DAB+/
FM/AM Radio
I am having problems getting the
DAB+/FM/AM Radio (January-March
2019; siliconchip.com.au/Series/330)
working.
I initially purchased the Micromite+
Explore 100 as a kit from your Online
Shop. I assembled it and connected the
recommended 5-inch touchscreen. To
test it out, I modified Geoff’s Graham’s
Super Clock (July 2016; siliconchip.
com.au/Article/10004) to run on the
Explore 100. It all worked well.
I then ordered the DAB+/FM/AM
Radio Board, again from your shop,
with all the components pre-mounted
in the IC1 area and I also purchased the
other surface-mount parts set. I then
assembled this board, less the optional
digital audio components.
I then assembled all the board into
the ‘stack’ with just the front perspex
panel. On powering up, one pair of
the audio transistors kept overheating.
Having read the letter and your reply
to another reader in the March 2019
magazine, I removed the 2.2kW resis-
tors from the ends of the diode and
this stopped the problem. I will fix
this properly after I’ve solved the fol-
lowing problems loading the firmware.
When I power up the radio, I get the
following messages in the start-up log:
Changing to AM
setting radio mode to... 0
radio reset, loading firmware...
LOAD_INIT failed
HOST_LOAD error! 1st pass
HOST_LOAD error! 2nd pass
Bootloader load from flash: 1197
LOAD_INIT failed
loading AM radio firmware from
flash...
done loading firmware from
flash.
booting radio...
booted.
I tried re-loading the data into flash
chip IC3 using the touchscreen con-
trols. No errors were reported on the
serial terminal, and it finished with
the “Done” message. But it didn’t fix
the booting problem.
I then used a PICkit 3 to re-load the
Explorer 100 with the full hex file
from your website. No errors were
reported, but the terminal program
seemed to indicate the baud rate was
wrong by printing strange characters.
I could not resolve this, so I re-load-
ed MMBasic from Geoff’s site. Then I
loaded the radio firmware (crunched)
from your website. I still got the above
error messages.
I also checked the MISO, MOSI and
SCK (SPI) tracks between the Si4689
and Explore 100 and its onboard PIC
chip. I found no short or open circuits.
I checked the voltage on the 3.3V rail,
both 1.8V rails, and the 5V and -5V
rails on the radio boards. They all
measured as expected.
What do you recommend for the
next step? (A. M., Eltham, Vic)- Before we had time to formulate a
response, we received a follow-up:
I used a CRO and multimeter to fol-
low the steps during the start-up pro-
cedure. Downloading the Si4689 data
sheet with flow diagrams, I could iden-
tify the steps in powering the chip up.
It soon became obvious that the reset
signal from pin 74 on the Explore 100
PIC was missing.
I checked this line and it was shorted
to ground. I couldn’t see any solder
bridges or other problems on the PIC
pins (100-pin QFP).
However, after lifting pin 74, the
pin tested OK. The track appeared to
be shorted to ground under the PIC
chip. I could not find the short, so I
cut the track adjacent to the PIC and
linked pin 74 to the track. Success! It
now boots and reports ‘No Errors’ on
the screen.
We’re glad you found and fixed this
fault. This could be a flaw in the PCB.
It’s uncommon, but it can happen, es-
pecially when tracks are very close to-
gether, or close to copper pours.
We don’t have as much experience
with four-layer commercial boards as
we do with double-sided boards; po-
tentially, faults are more common on
these. But many of the PCBs we pur-
chase are also pre-screened for elec-
trical faults, so it’s surprising that a
faulty board would end up with one
of our customers.DAB+/FM/AM Tuner
not booting
I purchased the PCB for the DAB+/
FM/AM Radio with the major parts
pre-soldered to the PCB. I loaded the
supplied HEX file into the micro us-
ing a PICkit 4.
All appears normal except no sta-
tions appear to be available, even
though I am in a good signal area for all
bands. I get the following errors on the
serial monitor screen during booting:
Waiting for CTS Timeout
Load Init Failed
Patch Bootloader error (multiple
times)
Can you please point me in the right
direction to get it working. (P. J., South
Australia)- These errors point to a communica-
tion problem between the microcon-
troller and the radio IC. With no (or
garbled) communication, no stations
will be found. We had similar prob-
lems with our prototypes at times,
which we eventually traced to bad
connections in the large 40-pin header
between the boards, as the pins were
not making proper contact.
Apart from checking that, we sug-
gest looking for problems on the
boards between the microcontroller
and the radio IC, eg, incorrectly in-
stalled or missing components, bad
solder joints or solder bridges creat-
ing short circuits.
DAB+/FM/AM radio
BASIC code not loading
I have been working on building
the DAB+/FM/AM Radio and today
got the Explore 100 board and dis-
play running.
I haven’t finished the radio yet, but
I attempted to upload the “DAB FM
AM Radio Firmware CRUNCHED.
bas” file into the Explore 100 board. It