Show Posts
Pages: 1 ... 3 4 [5] 6 7 ... 14
61  Forum 2005-2010 (read only) / Development / Re: Crystal uses (compared to ceramic resonators) on: July 05, 2008, 12:00:44 pm

The "recommended" 8 bit maximum error, even in double-speed mode, is an order of magnitude greater than the fundamental error of a resonator and well within any expected deviation. The maximum error is greater than even the worst case resonator error.
62  Forum 2005-2010 (read only) / Development / Re: Crystal uses (compared to ceramic resonators) on: July 05, 2008, 02:55:49 am
Ben, I agree with you 100% (which is why I make kits with resonators).

To be fair, the following illustrates the difference between resonators and crystals:
AWCR-16.00MDABL-16.000MHZ-B2
Price$0.18$0.27 (plus caps)
Tolerance0.5%0.05% (50ppm)
Temp Stability0.3%0.05% (50ppm)
10yr Stability0.3%0.05% (50ppm)

The worst case scenario (end of the temperature scale, 10+ years old, and worst sample) is about 1.1% (15.82MHz - 16.17MHz) while the crystal is about %0.15 (15.976MHz - 16.024MHz). Obviously you're unlikely to see this kind of error in either component. You'd have to look it up, but I believe NASA testing showed their resonators to be within 100ppm of the target frequency from the factory. It's also important to realize these numbers are based on a perfect board layout (and capacitor matching for the crystal, badly matched load caps can severely throw off the native frequency).
63  Forum 2005-2010 (read only) / Development / Crystal uses (compared to ceramic resonators) on: July 05, 2008, 12:13:58 am
For virtually every resonator based board, someone comments "Will there be a crystal version" or "I'd buy it, but it uses a resonator".

So, why would you like a crystal? What would you use it for?
64  Forum 2005-2010 (read only) / Development / Re: Where to find shield headers w/long pins? on: June 13, 2008, 04:24:18 pm
These are supposingly custom items that digikey magically assembles for you when you order them. Similar items are digi-reels and cable with the ends pre-soldered.
Based on the tooling marks from the ones I get, the 'magic assembly' involves cutting them down from a larger strip. They're out of stock because they don't know if it'll take them 2 seconds or 45 minutes to get someone to do it and they don't want to lose their on time guarantee for a large order because they can't cut one header on time... so they're out of stock but not really.
65  Forum 2005-2010 (read only) / Development / Re: Through hole socket for FTDI UART chip? on: June 04, 2008, 09:03:44 am
The QFN version is much smaller than a PLCC (think less than 1/4" x 1/4").
I think a test-socket is about the closest your going to get. Something like this (SOIC sockets are dramatically cheaper than the QFN variant).
66  Forum 2005-2010 (read only) / Development / Re: ISP Board ? on: May 30, 2008, 02:23:57 pm
Quote
I haven't understood yet if Atmel ┬ÁC usually *required* an external oscillator/resonator.
No, the ATmega168 includes in internal 8MHz rc-oscillator (which is /8 for 1MHz initially).
The Lilypad firmware will run correctly on boards with the internal oscillator, for NG/Diecimilla compatibility you need a 16MHz clock of some kind.
An additional caveat, once you've fused a chip for some sort of external clock, you'll need to either use an external clock during programming or use parallel programming to rescue the IC.

Atmels long shunning of internal resonators means most ATmega designs use one, even if they could have used the internal RC clock.
67  Forum 2005-2010 (read only) / Development / Re: ISP Board ? on: May 30, 2008, 02:06:46 pm
Prior to purchasing a ZIFDuino, I used virtually the same setup your describing. It's blogged about over here.

I switched to the ZIFDuino mostly because it's nice not to have a pile of wires.
68  Forum 2005-2010 (read only) / Development / Re: ISP/Programmer ? on: May 29, 2008, 05:42:30 pm
If you're only looking for hobbyist functions, suggest either the AVRISP MKII (about $35 from reputable places) or LadyAda's USBTinyISP, both are great programmers. If you can find one I'd even suggest the original (serial) AVRISP, these are cheap and just as good as the MKII.

If you're looking to move beyond just tinkering, the AVR Dragon is an excellent middle ground, it can debug a selection of smaller chips (ATmega168s included, IIRC) and can do high voltage programming for the smaller ATtinys or parallel programming for quicker throughput or for rescuing micros with incorrect fuses.
69  Forum 2005-2010 (read only) / Development / Re: boarduino 2 on: April 08, 2008, 01:41:45 pm
Very nice looking. I've been wondering when these would come out; we've been seeing them in your pictures for a while now.
70  Forum 2005-2010 (read only) / Development / Re: A breadboardable Arduino clone with onboard US on: April 12, 2008, 09:28:53 am
Quote
I like it, and I would buy one except that it uses a resonator rather than a crystal.  I hate that I have a decimillia tied up in my clock, but pretty much all of the cheaper boards won't work because of they use resonators
Hmm, in this case, a resonator is used due to a lack of space. If you were dedicated, a HC-49US sized crystal would certainly fit the layout, and two small caps could be soldered between it's legs.
Certainly some of 'the cheaper boards' do use crystals, I know NKCElectronics uses crystals in some of his Freeduino kits. My own MaxSerial board supports a crystal, and I'd be happy to substitute one in on request.
71  Forum 2005-2010 (read only) / Development / Re: A breadboardable Arduino clone with onboard US on: April 01, 2008, 12:51:45 pm
[size=16]iDuino kits are now available for sale[/size].
Please checkout the directions and then take your pick from the WebStore. The first 25 kits will ship immediately, any after that will be back ordered and ship shortly (one to three days as boards come from SMT assembly).



72  Forum 2005-2010 (read only) / Development / Re: A breadboardable Arduino clone with onboard US on: March 15, 2008, 09:42:57 am
The cap is indeed inside of the socket. In this case though, it's a very tiny PTH cap (same as the blue ones used around the socket). The pads are large enough to mount an SMT cap in there if the socket is much shorter, or underneath if you don't use a socket.

Quote
But given the shape - I'm wondering why not swap the F USB for a M, give it a (removable) enclosure with holes/standard sockets in the side, and turn it into a key drive form factor?  Keyduino?
Now the wheels are turning. I'm imagining the same design with a longer neck and a Male USB connector. Housed in an enclosure with 0.100 spaced screw terminals accessible through the sides and top. This would ofcourse require a CNC'd enclosure.
My only thought though is on usefulness; how useful is an arduino stuck directly to the USB port. On anything other than a laptop, it'd be stuck behind the machine somewhere and on a laptop it would need to be very tightly speced to make sure it didn't put too much stress on the USB port. The same enclosed design would work though with a regular USB-B connector and a short cable, allowing you to place the box on your desk.
Instead, I'm picturing more of a HardyDuino with a tough case, screw terminals, and some input protection. Much more suitable to deploying into harsher conditions, maybe with some outputs run on relays?
73  Forum 2005-2010 (read only) / Development / Re: A breadboardable Arduino clone with onboard US on: March 14, 2008, 01:24:03 am
Quote
When and how can we buy some?
I'm waiting for a few components to come in and I need to finish assembly directions, then I'll make them available in my online store as boards and kits.
A week to two weeks away I'd guess with a price around $20.

Quote
Are they tested yet?
Yes, kind of. Still waiting for the resonators to come in, so one has been tested running the Lilypad bootloader. Everything appears functional and the layout is viable.

On that note, a blurry picture of the first assembled unit, albeit with mostly surplus parts.



My largest task now is soldering FT232 chips; who would have guessed baking is a key aspect of hobby electronics now.
74  Forum 2005-2010 (read only) / Development / A breadboardable Arduino clone with onboard USB on: March 13, 2008, 03:59:06 pm



A box of these arrived from the PCB fairy this afternoon.

The design started out life as the Freeduino Through-Hole design and was hacked and squished until it fit into a vaguely DIP like form. At that point it was starting to look like a Boarduino, so I swapped two pins and ended up with the same pinout. They then spent 5 weeks in manufacturing and shipping (I'm cheap), and now they're on my work bench.

...Yes, I'm warming up the toaster oven right now.  ;D
75  Forum 2005-2010 (read only) / Development / Re: FT232 price jump on: April 07, 2008, 01:18:31 pm
Quote
Where are the FTDI chips made?
My BoL shows them made in Indonesia, but the company is located in the UK
Pages: 1 ... 3 4 [5] 6 7 ... 14