Say what's wrong with a PIC? They seem more than capable of powering some of our (fairly) capable projects...

Stu

My first digital camera had a serial port to get pictures off it. There weren't any USB ports on my computer to plug a card reader into, not that you could buy a cheap CF->USB adaptor in those days.

I actually used to use IrDA to get stuff off it instead. You just put the camera in PC mode and left it on the desk pointing at the screen which had a little IrDA port stuck underneath.

My first camera had SmartMedia cards and it was before USB card readers, so I had a 3.5 inch floppy based card reader. Insert SmartMedia card into reader, insert reader into floppy disk drive. I think I've still got it in a box somewhere.

I've never got on with them, sure people have done some impressive stuff with them, but we've consigned (barring a couple of design we did recently) 8 bit micros to history. Incidentally, the USB on the pics is good, LOADS of endpoints on them which is something that our favoured ARM processor is lacking.

I've also never found a C compiler that works properly, I normally end up finding incorrect code generation almost immediately, I don't have time to hand hold the compiler with every line of code I write and given the problems with incorrect code generation I'd be very worried about what could lurk inside shipping firmware.

The last compiler I used was microchips own C compiler and I managed to get that to generate incorrect code with a convoluted type cast after only a few hours of coding, not a good start.

I've never personally seen a single compiler problem with gcc for arm and the development environment I use (crossworks) is fantastic, I seriously have no idea how people use MPLAB because after 2 minutes of using it I was ready to tear my hair out...seriously...it's 2009 and they have workspace and project windows as MDI children rather than as separate panes.

I'll concede that most of my gripes come not from the PIC micro itself but from the supporting tools. Rowley do have a version of crossworks for pic and I'm assuming it's probably of the same quality as crossworks for ARM, so if I ever need to use a PIC in anger again they'll probably be getting an order from us, but thankfully I should never have to touch the source to the firmware on the PIC stuff ever again.

Well that explains it ! We program in assembly and are admitedly moving on to ADI Blackfins (in C and C# I believe)for another project so the 8-bit micros are certainly not always the best but they have their place.

Stu

Speaking of 8-bit micros and other ancient stuff, my dropped-out classmate from university write/sells excellent "everything" development kits for quite reasonable prices. Mention my name for fun.

Cheers

I've now updated the design with USB audio and whip antennas for a little better range. I realized that the radios in these are really only Bluetooth class 3 devices, so range is limited to 30 feet or so. Still, it's cool to be able to plug these into USB and stream anything playing on your PC to a high quality stereo with no loss of quality and one cable for power and signal. The 44.1 kHz sampling rate restriction remains, but I'm working on that.

Anyone interested once the last of the bugs get worked out?

Stuart

It looks like I've worked out the bugs in the code. The device can now stream 44.1 kHz, 48 kHz via USB or TOSlink and Dolby Digital and DTS via TOSlink over roughly 30 feet to a TOSlink output.

Is there anything else anybody would like to see before commit to a design?

Stu

DVI/HDMI?


(ducks and runs for cover)

I thought I'd update everyone on the status of this project. I decided to add quite a few features to make it more useful. Perhaps the most significant is that the power has been increased from 0 dBm to 25 dBm (320 milliwatts) for much better immunity to ambient WiFi signals. I also threw in analog in/out and some other tweaks!

It's currently being built up in Colorado. I'm hoping there are no major faults with the design and that the relatively simple firmware develops quickly.

I'll post updates as they develop.

Stu

Sounds like it is progressing well Stu, is the receiver still powered by a wall-wart or have you got it running on battery power now? If so (battery), will there be an option for both e.g. battery power for headphone usage and a wall-wart for longer term hi-fi connections? This is assuming the receiver has enough output to drive headphones. Apologies if this has been covered already, I have just caught up with this thread after a few weeks absence and it is a bit late here to go back and read through it again. Thanks.

This device wasn't really conceived as a portable solution- more of an unobstrusive semi-permanent one. It certainly can run off of batteries via the power jack but with such a high power radio, I wouldn't expect you would get over 10 hours from 8 AAs. As for driving headphones, it's not designed for that but it has a pretty high quality DAC with a high voltage output so you may have success with many headphones.

It this answers your questions!

Stu

Did you have fun reading the USB audio spec stu? What a document that one is! I've just had the misfortune of reading it as I've just added a "PC interface" to our doppler radar (aka speed detector) interface and decided the nicest way of doing it was to pass the "doppler audio" straight into the "PC".

All I can say is that I'm glad that they include sample descriptors in the usb audio document otherwise I think I'd still be trying to decipher what exactly is needed in them!

Thanks Stu, one more question:
Now that the radio power output has been increased, how much more range can you get over the 30' that was previously mentioned?

We glossed over some of the general USB specs but since the actual code is executed in silicon I guess the specifics of the audio protocol were of little concern. You make it sound like a great read though. I might just check it out!

By the way, the USB org has decided that mini AB connectors such as we have used in our prototypes are illegal now (they decided this after development started). So now if we ever want to certify our device we must go to a micro AB connector. Yay!

Stu

We'd have to test it first but I would guess a solid 100% pop free performance could go to roughly 75-100' with a still very usable link reaching out to 300-500'. This all depends a great deal on the application as well as ambient RF environment.

Stu

That sucks. I hate the micro connectors. They're really hard to align when you're plugging them in.

I hate them too. I thought the minis were a good compromise between size and user friendliness, but the USB folks thought it was too confusing to have all the different connector types out there. Plus it seems the micro design is more durable.

Edit: It seems this only applies to portable devices using the "USB On the Go" logo which this isn't because it cannot be a host as the standard dictates and has actually been enforced since May 2007, so I just missed it during board layout. Still it looks like they outlaw the use of Mini-AB connectors in favor of the less flexible Mini-B.

Stu

That's good since I prefer rock, blues and swing, to pop.

Seriously, that is a pretty good range, enough for any room or house even!

Hi All. I'm just posting an update for those interested. We've gotten the high power version back from Colorado and populated the remaining 'easy' parts. We haven't yet tested the max range with the device but have observed 75 feet of rock solid performance through multiple walls and roofs.

We've also gotten the analog output to work on the receiver side. We are quite impressed with the sound produced by this DAC even with a 300 mW transmitter less than an inch away. The only issue was an annoyingly vague labeling of the DAC outputs as 'Output A' and 'Output B' which wasn't as we thought it would be. Thankfully we were able to swap them in software.

We haven't been able to test the ADC on the transmitter side due to a vendor issue with the mini-optical jack but hope to rectify that soon.

Left is the software routine and any remaining hardware tweaks that may be needed.

Stu

That wouldn't be Sparkfun would it?

No although we did have them process a pool order to Gold Phoenix once with this project. AFAIK they don't offer assembly services. We would have used them again save for the fact that the requirements for the PA layout didn't fit the design constraints.

We had the fine pitch QFNs, 0402s and some miscellaneous other parts machine placed and baked by Advanced Assembly in Aurora, CO. They do top notch work with quick turnaround time.

A few months back we had our pick and place machine commissioned, seriously impressive to see it banging down chips at the speed it does, it's a revelation having complete control of the manufacturing process from start to finish now.

Can you make your own boards in-house too? Some of those laser-based systems look pretty impressive for low volume prototype work.

Stu

You mean the LPKF machines? Some of those are pretty nice....and with hefty price tags to match!

We have a CNC machine which was built for us which is extremely accurate, if we have a need to prototype a circuit, generally we'd use isolation routing and do a test layout that way. (http://empegbbs.com/ubbthreads.php/topics/308403/4)

We did use to do a lot of prototyping through pcb pool, but we have found a chinese PCB manufacturer who gives us many more boards for not much more than we were paying for a single prototype from pcb pool, so we tend to prototype through them now and get production boards for other products bundled in.

The youtube video below is the next board that we're about to get the pick and place machine to do, trust me, soldering all those surface mount leds is not fun!

http://www.youtube.com/watch?v=E7huEauTA2o

Yep. Those are the very same. Last I saw some of their more tasty machines were north of US$30K.

Stu

That looks like one of those speed-sensing warning signs you find in built up areas and accident blackspots around the UK?

If so, can you answer this: Are they typically set just below the speed limit? I.e. 29MPH in a 30MPH zone? My reason for asking is that I am very careful to keep to the speed limits in residential areas, typically 30 and 40MPH zones, and even then a lot of them flash up the speed limit (not the actual measured vehicle's speed) seemingly to chastise me for speeding! With one in particular that I go past every day, I know that if I go past it at 25MPH it won't illuminate.

To be honest, I have no idea how they (i.e the councils) select their trigger speed, it's more than likely that they do set them lower by a percentage because the indicated speed on your speedo will be higher than your actual speed. It's also possible that they set them lower to provide some buffer with regards to the cosine error (which is always in the motorists favour) so that a slightly incorrect installation will still be spmewhat accurate.

All I can tell you is that while we were developing this and its companion doppler radar board, we got some long stares from motorists as they drove past us!

Neat, but how many speedometers are calibrated in hex.

Do you suppose I could convince a cop that I was going 100 MPH because I thought the speed limit was 0x65?