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Topic: Your latest purchase (Read 116 times) previous topic - next topic

Nick Gammon

It would be interesting to experiment with things where speed is the essence, like writing VGA output.

Running at 24 MHz is a 50% speed boost, which isn't too shabby.


you should look at some of the xmega's, arduino support is out there, no idea how perfect it is with libraries and whatnot, but the core is there to write your own. Anyway those things come in 8 and 16 bit flavors clocked up to 32Mhz.

I have a small strip of them and some 25.175Mhz crystals, the dot clock speed of 640x480 VGA, which easily divides for sync signals (not specificly for generating 640x480 graphics)

Nick Gammon

I don't particularly care about recompiling the core because only a small number of things will be out. For example, baud rates, but you can compensate for that. And you could compensate for the readings returned by millis().




So you just popped out the 16Mhz crystal and replaced it with the 24Mhz?

Nick Gammon

This was on one of my breadboard models, but yes, I shoved the crystal in, and reprogrammed the fuse to not use the internal oscillator, as shown:

The ICSP programming cable is visible.


So I can use any existing 16Mhz bootloader (example: from Adafruit) with a 20/24 Mhz crystal, right? -- millis() timing may be off, but all the others should work fine as is.

Nick Gammon

The thing about the core is, the processor doesn't really know what speed it is running at. So for example if you use the 8 MHz internal oscillator everything will just be half the speed. So a 9600 baud rate for the serial port will really be 4800 baud. And delay (1000) will really delay 2000 mS.

Now for the bootloader, the problem will be it expects a certain baud rate. However if you change boards.txt to reflect the difference, it should work. So for example, for the Uno:

Code: [Select]
uno.name=Arduino Uno

Since the upload speed is normally 115200 you would need to increase that to 115200 * 24 / 16, which is 172800, assuming the USB chip can handle that speed.

However in my case I programmed with ICSP (not the bootloader) so that didn't apply. So, disclaimer: I didn't test with a bootloader.


Could you bootload at one speed and run at different?
I find it harder to express logic in English than in Code.
Sometimes an example says more than many times as many words.

Nick Gammon

Absolutely. All the bootloader does is put the program into program memory. You could then turn the power off, replace the crystal, and power it up again.

Papa G

One of my offspring got one of these for Christmas. Have any of you seen them? Made in the UK and pretty nifty.



Mar 04, 2013, 10:51 pm Last Edit: Mar 05, 2013, 01:41 am by focalist Reason: 1
Since when is Radio Shack reasonably priced?  Went to the MALL store and got a Seeed Studio Proto Shield for $9.99!

Okay- Credit where credit is due.

Seeedstudio-- the protoshield kit is awesome.  This is a great deal at ten bucks.
I expected the board headers and such, and not much else.  However, they also toss in an extremely useful collection of common components:  two red and two green LEDs, a bicolor LED, resistors for the LEDs, a 10k pot, two 40-strips of male pin headers, a 40-strip of female header, a 40-strip of long male headers, spare spacers, four tactile switches and two slide switches, and a USB socket.  That's a heck of a lot for ten bucks!!!

I will be grabbing these again!
When the testing is complete there will be... cake.


I finally bought an ISP for burning bootloaders, lol. Its apparently based on the USB ASP. Cost $7 on ebay.

I also bought a used server rack with UPS, 6 servers, a DAS, and a bunch of other junk. I'm probably going to use it to test an arduino based datacenter monitoring system.
"Anyone who isn't confused really doesn't understand the situation."

Electronic props for Airsoft, paintball, and laser tag -> www.nightscapetech.com


Just got a partial shipment on what may be my last order from DX (DealeXtreme).
Got 50 40-pin header strips (steel, not brass pins), 10 keychain SD-micro/USB adapters and 3 IR signal receivers and a bag of jumpers. Still waiting on 10 2 mW laser modules (because at 45 cents ea, I'll make a use), 10 snap-in RJ-11 modular jacks, and 2 female-female 40 cm DuPont cables.

Well, I might order disc batteries from them but I can't say about that either.
I find it harder to express logic in English than in Code.
Sometimes an example says more than many times as many words.


24, yes 24 bit ADC module for less then $10. Let me count the bits, 1,2,3...yes 24 bits in all. So no need to have to amplify externally how level Wheatstone bridge type sensors, just read the millivolts, hell microvolts directly and still have more resolution then arduino's wimpy 10 bit ADC has.

We will have to see how the low noise performance of this module ends up with, as usually in the real world it's nearly impossible to actually be able to fully utilize 24 bits of resolution.



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