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@Sharkzz
I think what you're talking about is more related with this thread (there are more about the same subject of using external controls, even a PC to control a regular transmitter). This thread iis about the opposite: Using a regular TX as a PC joystick to control a PC appliance (typically, a RC flight simulator). |
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Riverside, CA
Joined Jul 2006
2,544 Posts
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been a few years since I made one of these, so I decided to make a few more using Alessio and Andreas most recent build (from 2007!!) which cuts out a few resisters and has a nice pcb.
I am tired of paying $4 a crystal at the local electronics wherehouse, so I ordered all of my parts from digikey. The crystals I ordered from Digikey: (http://parts.digikey.com/1/parts/395...ap-ats040.html) state they have a 20pf load cap. If I use them in the circuit, they cause a power surge on the USB hub, and nothing works. Plug in one of my series crystals ($4!!) which states that it load cap is "series" and it works fine. Anyone with more electronics experience than I able to help with these digikey guys work? I imagine I need a different capacitor value on each end of the cystal then the usual 22pf or 27pf. Thanks! |
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Riverside, CA
Joined Jul 2006
2,544 Posts
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Yeah, I thought that too. Tried a straight wire across on both leads to ground on the breadboard, and no luck.
I've been toying with Pics for about 5 years, and I never knew until now about "load capacitance" and putting crystals in series vs. parallel: http://www.oscilent.com/spec_pages/P...t/Load_Cap.htm Looking at that first equation, and assuming the stray capacitance of the circuit (Cs) is about 5 pF, it looks like two caps at 30 pF might give me the load cap I need to get 4 Mhz out of these crystals. Or, if I use this equation: http://www.crystek.com/microwave/app...ateLoadCap.pdf with Cin and Cout as 5pf, and Cs is 3pf, then I get 29 pF. I tried some 27pF caps that I have, and that didn't seem to do it. Just for experiment's sake, I'll probably pick up some 30 and 32 pF to see if trial and error will help any of this theory make more sense. Either way, I think I put them IN SERIES with the crystal wires as usual. I should have taken some electronic engineering classes in college... |
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Riverside, CA
Joined Jul 2006
2,544 Posts
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Best info yet is actually on Microchip's manual:
http://ww1.microchip.com/downloads/e...doc/33023a.pdf Chapter 2 talks more about oscillation than I ever wanted to know! Either way, I think I need to toy around with different values, and making C2 > C1 might help oscillation start up faster. |
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Hampshire, UK
Joined Sep 2000
1,287 Posts
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Quote:
What version of code? 3.3.4? I might have to program a new chip - just to ensure that I have the latest - although as I mentioned it works fine on my XP machine. My Windows 7 Home Premium machine is a Sony Laptop. Other USB devices work fine - but the interface never gets discovered (doesn't even appear in Device Manager) - so never even get a "can't recognise device" error message. ![]() Malc: Yup, I understand that it's seen as a HID device (and shouldn't require anything else). The laptop I'm using is brand new, maybe I'll have a play with the power settings.. |
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Riverside, CA
Joined Jul 2006
2,544 Posts
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3.3.4, yes. Although I don't know that the code versions should matter. If one sees it, another should.
Other option is take a walk into the local computer retailer or a friend's house and plug it into one of their windows 7 machines. If it pops up, you know its something at a local level. Toshiba laptop with W7, Compaq with XP, and HP with Vista home all detect both the built one and the breadboarded versions without an issue. |
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Hampshire, UK
Joined Sep 2000
1,287 Posts
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Quote:
Looks like I've got to get a new PIC programmer. My last one was a serial port one, and since upgrading the PC I now need a USB one! *sigh*. |
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