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[Reply #15 on:]

Thank you!  This will come in very useful. 

I'm interfacing to a 128x64 GLCD and I could use more speed to display multiple spectrum bar graphs faster.

[Reply #16 on:]

If you want, you will find that most of them will run at 32Mhz @ 5v.

Pretty amazing.

[Reply #17 on:]

Hmm. Time to revisit my VGA output sketch. If I can get it to run that fast I could get somewhat higher resolution.

Does it get hot?

[Reply #18 on:]

Well that idea will have to wait. Don't have any 24 MHz crystals. Nor does my function generator output above 20 MHz.

Oh wait, found 5 x 24 MHz crystals on eBay for $1.41 + free postage. Kind of unbelievable but whatever. Worst I will do is lose $1.41.

[Reply #19 on:]

Hi Nick,

No it doesn't get hot at all. I test it now for 4 hours in a row and i found out that serial, adc conversion and eeprom read/write works well.
No trouble so far. I've change one other board and put it to the test.

I will see in the morning if it goes well.

[Reply #20 on:]

I ordered 100 x 20 MHz crystals for $5.69 as well.

We'll see what happens with that one.

[Reply #21 on:]

Nick,
I get crystals from Tayda:
http://www.taydaelectronics.com/crystals-resonators-oscilliators/crystals.html
They have pretty low prices on everything they sell and their shipping is pretty
low as well.

--- bill

[Reply #22 on:]

Thanks Bill.

If the worst comes to the worst, they can become stocking-fillers next year.

"What, this, Dad?"

"It's a crystal, darling"

"Cool!"

[Reply #23 on:]

Today I tried getting an ATmega328P-PU to work at 20MHz. I downloaded the optiboot.zip file and copied the contents to my optiboot folder (I'm using Arduino-1.0.3 on linux). I made the necessary changes to boards.txt. I then started the Arduino ide and selected the "GVI High Speed (5V-20MHz-250k Baud)" board. Burned the bootloader with an USBasp, uploaded without errors. I then hooked up my ftdi usb/serial converter to the board and tried uploading the blink sketch. But no luck, it can't get serial communication. I tried another ftdi usb/serial converter but I got the same error:
avrdude: ser_recv(): programmer is not responding
avrdude: stk500_recv(): programmer is not responding

Just to be sure I plugged the chip in another board with a 16MHz crystal. Bootloaded the Uno bootloader and uploaded a couple of sketches, no problems there, so the chip is fine.

When I try uploading a sketch the led on pin 13 blinks a couple of times. So can I assume that the bootloader is working?

[Reply #24 on:]

What is the entry for boards.txt for the board you selected? In particular, the upload baud rate?

Where did you get the bootloader which expects to run at 20 MHz?

[Reply #25 on:]

From a previous post in this topic: http://arduino.cc/forum/index.php/topic,137902.msg1041577.html#msg1041577

I copied the code from that post to my boards.txt file, baud rate is set to 250000.

[Reply #26 on:]

Hmm. Well I was getting strange error messages if I had a non-standard baud rate:

Code:

avrdude: ser_setspeed(): tcsetattr() failed
avrdude: ser_open(): can't set attributes for device "/dev/cu.usbserial-A900gcHm": Invalid argument
ioctl("TIOCMGET"): Bad file descriptor
avrdude: ser_close(): can't reset attributes for device: Bad file descriptor

[Reply #27 on:]

I get this:
Using Port                    : /dev/ttyUSB0
         Using Programmer              : arduino
         Overriding Baud Rate          : 250000
avrdude: serial_baud_lookup(): Using non-standard baud rate: 250000
avrdude: Send: 0 [30]   [20]
avrdude: Send: 0 [30]   [20]
avrdude: Send: 0 [30]   [20]
avrdude: ser_recv(): programmer is not responding
avrdude: stk500_recv(): programmer is not responding

Uploading sketches with the USBasp works.

[Reply #28 on:]

Did you change the xtal to a 20MHz one?

[Reply #29 on:]

would you not just change the crystal to a faster one?
do you really need to change the code?

devobtch