Pages: 1 ... 31 32 [33] 34 35 ... 67   Go Down
Author Topic: Your latest purchase  (Read 112108 times)
0 Members and 1 Guest are viewing this topic.
Global Moderator
Offline Offline
Brattain Member
*****
Karma: 503
Posts: 19095
Lua rocks!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

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.
Logged


SE USA
Offline Offline
Faraday Member
**
Karma: 41
Posts: 3783
@ssh0le
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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)
Logged


Global Moderator
Offline Offline
Brattain Member
*****
Karma: 503
Posts: 19095
Lua rocks!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

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().
Logged


SE USA
Offline Offline
Faraday Member
**
Karma: 41
Posts: 3783
@ssh0le
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

https://github.com/akafugu/Xmegaduino/blob/xmegaduino/README.md
Logged


Offline Offline
Sr. Member
****
Karma: 9
Posts: 296
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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

Global Moderator
Offline Offline
Brattain Member
*****
Karma: 503
Posts: 19095
Lua rocks!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

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.
Logged


Offline Offline
Sr. Member
****
Karma: 9
Posts: 296
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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.
Logged

Global Moderator
Offline Offline
Brattain Member
*****
Karma: 503
Posts: 19095
Lua rocks!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

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:
uno.name=Arduino Uno
uno.upload.protocol=arduino
uno.upload.maximum_size=32256
uno.upload.speed=115200
uno.bootloader.low_fuses=0xff
uno.bootloader.high_fuses=0xde
uno.bootloader.extended_fuses=0x05
uno.bootloader.path=optiboot
uno.bootloader.file=optiboot_atmega328.hex
uno.bootloader.unlock_bits=0x3F
uno.bootloader.lock_bits=0x0F
uno.build.mcu=atmega328p
uno.build.f_cpu=16000000L
uno.build.core=arduino
uno.build.variant=standard

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.
Logged


Pittsburgh, PA, USA
Offline Offline
Faraday Member
**
Karma: 98
Posts: 4813
I learn a bit every time I visit the forum.
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Could you bootload at one speed and run at different?
Logged

I find it harder to express logic in English than in Code.
Sometimes an example says more than many times as many words.

Global Moderator
Offline Offline
Brattain Member
*****
Karma: 503
Posts: 19095
Lua rocks!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

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.
Logged


Dallas, TX
Offline Offline
Sr. Member
****
Karma: 10
Posts: 318
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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

http://www.mikromart.com
Logged

Boston Suburbs
Offline Offline
God Member
*****
Karma: 16
Posts: 955
I am above your silly so-called "Laws", Mister Ohm.
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

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!


* 20130304_164916.jpg (1971.08 KB, 2048x1536 - viewed 17 times.)

* 20130304_194048.jpg (1657.96 KB, 2048x1536 - viewed 12 times.)
« Last Edit: March 04, 2013, 07:41:19 pm by focalist » Logged

When the testing is complete there will be... cake.

Maine
Offline Offline
Sr. Member
****
Karma: 14
Posts: 418
Caution: Explosives in use.
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

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.
Logged

"Anyone who isn't confused really doesn't understand the situation."

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

Pittsburgh, PA, USA
Offline Offline
Faraday Member
**
Karma: 98
Posts: 4813
I learn a bit every time I visit the forum.
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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.
Logged

I find it harder to express logic in English than in Code.
Sometimes an example says more than many times as many words.

Left Coast, CA (USA)
Offline Offline
Brattain Member
*****
Karma: 361
Posts: 17303
Measurement changes behavior
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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.

http://www.ebay.com/itm/121022291106?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

Lefty
Logged

Pages: 1 ... 31 32 [33] 34 35 ... 67   Go Up
Jump to: