Today I built three boards using parts from the production batch with the second, and hopefully final, spin.
All worked first time, and sensitivity was as expected with the LNA now integrated, although I have noticed that this batch seem to hang after five or ten minutes of streaming, unlike the version first PCB spin, so I will be looking into that. The firmware is identical so it’s a bit of a head scratcher at this stage.
The three QFNs were reflowed and I hand soldered the other parts: a long story as to why I didn’t reflow the lot, but basically it was down to the four dimensional logistics of where I was this weekend, and at what time I could do what!That 5p coin is about the same size as a US dime. Blow torch soldering not compatible!
If you look closely, you’ll see the orientation of the middle chip on the bottom dongle is wrong compared to the others – I had to lift at re-orientate the device. This is where you need a hot air iron. Now I like Weller stuff as you can see in the photo below, but for a hot air gun either you can pay £700+ for the Weller or £65 for one on ebay from China. I chose the latter, and it’s saved my bacon on a couple of occasions. If you’ve ever been to the electronics market in Hong Kong, you’ll have seen vendors at market stalls using these to re-chip mobile phones. I was in total awe the first time I saw this. Recommended, I wouldn’t be without one now.
Hand soldering I can do anywhere, but reflow I can really only do in the static workshop. Here is the “mobile” workshop…
The mobile workshop consists of four soldering irons including tweezers and a hot air iron invaluable for rework. A stereoscopic microscope is essential! A comms test set, four channel scope, laptop, DVM, assorted aerosols, PSU, test radio, magnifying lamp, in circuit emulator, test jig and a selection of hand tools fill the rest of the table.
What is the actual current draw?
Current draw is 150mA in normal operation. Before USB initialisation however, the tuner and codec are held in a low power state to keep the aggregate current draw under the USB spec’s prescribed 100mA limit at this stage.
Of course, if you make the elementary error that I made during construction the other day, you barely see 15mA…
Love the mobile workshop, what circuit emulator software are you using to design and develop this dongle?
I am looking at designing and emulating Audio, DSP and SDR circuits for my own HPSDR, SDR and DSP projects, but no idea what software would help me get started. I have just looked a CircuitLogix and would appreciate your suggestions. Need to develop circuits for frequencies from 144 MHz up passed 10 GHz if possible? The higher the frequency been received the better. Interface for the receiver will be gigabyte ethernet rather than USB.
Many thanks in anticipation of any reply,
I hope this cones out ok as I’m doing it from a cellphone. The debugger I use is a Real ICE predominantly, but I do also use a pickit 3. The Real ICE I am sure I’m not using to its maximum capacity but it does allow software breakpoints unlike the pickit 3 which only seems to allow hardware breakpoints.
However regarding Ethernet, be careful in the microcontroller domain: in my experience, there is rarely any point to support 100mbps as the poor old MCUs simply can’t keep up. They may ‘support’ 100Mbps, but they won’t maintain anywhere near that data rate.
Thanks for the reply and the additional information on the microcontrollers using ethernet, will have to be careful there. HPSDR ARE USING THE Altera Cyclone III FPGA connected to a Gigabit Ethernet PHY and iTS working well at medium speeds, like you with the dongle this used default drivers too. I have just placed an advanced order for the Metis http://openhpsdr.org/metis.html but now need to build my SMD back plate, now I know what you feel like working with ultra small SMD components, lol.
OK on the software, Real Ice has much potential and a good direction to take,I don’t like using hardware breaks so will stay away from pickit3 for now.
Everyone is following your development of the dongle with great excitement, been a long time in coming seeing this much excitement in the AMSAT world. I can imagine Ron Broadbend looking down at you and patting you on the back saying well done. I have had a few schools and colleges students asking how to hear FUNcube thanks to your great ideal and development of the dongle.
Take care Howard, and thanks for the feed back too.
I must have been really tired when I typed this reply at 03:00 hours, I typed hardware breaks, when I should have wrote setting hard and soft break points in running and executing the code. Takes me back to my university programming days again doing SmallTalk, Java, Borland C++ and assembly code. Remember how easy it was to make an error in code and create never ending loops?
David, thanks for the heads up on the hot air gun and soldier station, saw you can order this particular one and other similar stations from on ebay from UK £99 or Hong Kong $99 plus $35 international air freight mail and customs tax. How much did Royal Mail customs charge you David? As I have several HPSDR Atlas etc. SMD boards to assemble, I just ordered one too. Cheers, Chris
I bought a hot air tool about a year ago. Very useful indeed. For those who don’t have them. If you take a small piece of tin and cut a hole in it just the right size you can remove one of those chips using a standard paint stripper gun – carefully. I used this method to remove a DDS chip that I had misaligned. That was several years ago before I got the hot air tool.
They are also great for heatshrink when used at a low setting.
Certainly agreed there. The one I have is sold by allstar-seller on ebay “SMD Rework Soldering Station HOT AIR GUN & Solder IRON”, on a $99 buy it now. It took a couple of weeks to arrive. It comes with spares and several different nozzles for the hot air and bits for the iron. I even find the fine pitch bit of the soldering iron better than my Weller for odd bits of touching up. Although the hot air is only used occasionally, I can’t think how else I’d be able to rework a misaligned powerpad QFN without either heating up the whole board or ruining the PCB.
Is there something up with the site. It’s loading up pretty slowly for me. Someone else experiencing this?
Apologies, some of the underlying images are very hi res.