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 by mac ¦  Fri Jan 29, 2010 1:59 am ¦  Forum: AVR Microcontrollers ¦  Topic: multiplexed 4-digit 7-segment display ¦  Replies: 12 ¦  Views: 5500

If you are displaying from interrupt, you have to make sure that the variable(s) you use to store value to display is updated atomically: IT: Get value, do display work. Main loop: Start reading ds1820 If result is ok: convert value to value to display or: set value to error (but why?) disabling IT ...

 by mac ¦  Fri Jan 29, 2010 1:49 am ¦  Forum: PCB Design Questions ¦  Topic: Finding a low cost oscilloscope ¦  Replies: 23 ¦  Views: 12934

For pure digital work, I prefer to use my zeroplus logic analyser. Great for decoding purpose and 100MHz internal clock with 32k trace for the lower end. That's also the reason why I use an usb scope, I already have a dedicated laptop* for the logic analyser. * this solve also the sharing ground pro...

 by mac ¦  Wed Jan 27, 2010 8:24 am ¦  Forum: PCB Design Questions ¦  Topic: Finding a low cost oscilloscope ¦  Replies: 23 ¦  Views: 12934

USB scope are quite ok, but are always expensive compared to cheap chinese scope (rigol, owon). I have a DSO5200, quite nice but suffers from inferior software and customer service, and also a nasty timebase bug (one timebase is false: 320ns/div instead of 400ns). The rigol scope (DS1052) is pretty ...

 by mac ¦  Thu Jan 21, 2010 4:12 am ¦  Forum: Code ¦  Topic: Debouncing a momentary switch ¦  Replies: 3 ¦  Views: 6485

You should use a mix of interrupt/polling. For detecting switch when running, use polling and debounce it. When the decision is taken to go into sleep/powersave mode, program external interupt on pin. When the interrupt fire, this basically mean that the switch is closed, or beiing closed (or EMI). ...

 by mac ¦  Thu Jan 07, 2010 9:10 am ¦  Forum: SparkFun Site Questions/Comments ¦  Topic: Not a good sign for free day ¦  Replies: 419 ¦  Views: 74130

it's $100k of value for customers, but not $100k on spending for SFE. My best guess is that's well below 25k, excluding new IT spending.

 by mac ¦  Wed Jan 06, 2010 7:35 am ¦  Forum: New Product Ideas ¦  Topic: 2/3A battery holder ¦  Replies: 2 ¦  Views: 694

Well, I am outside US, so no digikey :(
I can get them from Farnel, but minimum order and S&H are far exceeding the price of the holder itself or sparkfun S&H fee...

PS: hey I just checked digikey homepage, they have now a french-friendly site. S&H free for 100$+ orders...

2/3A battery holder

 by mac ¦  Wed Jan 06, 2010 5:29 am ¦  Forum: New Product Ideas ¦  Topic: 2/3A battery holder ¦  Replies: 2 ¦  Views: 694

Hi, I think this could be a nice product to add: an 2/3A cell holder (for CR123 battery). This format is quite popular for 3v lithium and now 3.7v li-ion cell. But holders are very hard to find. I have found some surplus 2/3AA holder (cell is smaller in diameter), they can be used after bending the ...

 by mac ¦  Thu Dec 17, 2009 6:40 am ¦  Forum: SparkFun Product Questions ¦  Topic: Oscilloscope Advice Please :) ¦  Replies: 9 ¦  Views: 8007

Second round: I switch back to latest v6 software (6.0.0.3). The ETS glitches are gone, so it's quite usable. I measure a 5ns rise time of a 1MHz square wave correctly. No more issue also when switching on/off channels and ETS. The FFT is much better, and less buggy (no 2nd hamonic reported as the f...

 by mac ¦  Thu Dec 17, 2009 4:26 am ¦  Forum: SparkFun Product Questions ¦  Topic: Oscilloscope Advice Please :) ¦  Replies: 9 ¦  Views: 8007

As promise, a quick test of DSO5200USB from Hantek. Test setup: Generator: Agilent 33250A Note that Agilent generator is not very good for noise and jitter issues. Reference scope: Agilent MSO6054A (50ohm connection). Hantek is using its standard 1/1:10 probe. Hooked on a dell D630 in usb2.0 connect...

 by mac ¦  Wed Dec 16, 2009 2:28 am ¦  Forum: SparkFun Product Questions ¦  Topic: Choosing A Scope And Logic Analyzer ¦  Replies: 5 ¦  Views: 2384

Quite decent specs, I had bad experience of HP at engineering school as we had 1Gh/s equivalent sampling which where in fact ~50MSa/s. Beware that scope will never compete with logic analyser, unless they have HUGE memory. But digital input like on the HP could be convenient also to add more digital...

 by mac ¦  Tue Dec 15, 2009 2:31 am ¦  Forum: SparkFun Product Questions ¦  Topic: Choosing A Scope And Logic Analyzer ¦  Replies: 5 ¦  Views: 2384

I renew recently my measure setup (from an old Metrix 530 2x20Mhz scope). I used to more-than-decent tools at work (Mixed DSO/Logic agilent 5Ga/s, dedicated big logic analysers). I discard quickly rigol scope, very attractive from the sampling point of view, but the puny screen won't do it for me (a...

 by mac ¦  Thu Dec 10, 2009 4:06 am ¦  Forum: SparkFun Product Questions ¦  Topic: Soldering iron recommendation ¦  Replies: 18 ¦  Views: 6792

At work I use weller station for small SMD rework: few components and patches, but on 0201 SMD it's quite challenging (binocular required). At home I use a CSI 2A soldering station. Quite fine for hobby use, but not built like a weller. I know it's not rated for lead free use, but there is no proble...

 by mac ¦  Wed Dec 09, 2009 5:37 am ¦  Forum: Wireless/RF ¦  Topic: nRF24 in low temperature environment ¦  Replies: 5 ¦  Views: 1186

Yes I know that nRF are rated to -40, but I also know from experience that it doesn't mean anything, especially for RF subsystems.
Since it uses standard 60ppm crystal, I just want to make sure that temp differences are ok.

Anyway, I have ordered some nRF24L01 and nRF2402 to play with.

nRF24 in low temperature environment

 by mac ¦  Fri Dec 04, 2009 2:34 am ¦  Forum: Wireless/RF ¦  Topic: nRF24 in low temperature environment ¦  Replies: 5 ¦  Views: 1186

Hi all, I have in mind a project which involves a set of nRF chips used in very short range (<5m) but in quite harsh condition: transmitter temperature may vary from -10C (14F) to 37C(98F body temp), and receiver may come less than -10C. So this means that both set could either operating at same (lo...