8 replies to this topic

[StefanUSMC]

Is there any way to get 25Mhz clock from the mini? I see that the ND+2 has this on PA8. I am going to be integrating the mini with a ENC28J60, and will need a 25Mhz clock for it. I have been a software guy all my life, so hardware is a bit above my level of expertise. The datasheet for the ENC28J60 has an example oscillator circuit, but I have no idea how to identify if, or what type, of series resister I would have to use on a strip cut crystal. Any direction would be appreciated.

 

Thanks,

Brandon

[Chris Walker]

Hi StefanUSMC, Netduino Plus 2 does forward the clock generated with the 25MHz crystal to the ENC28J60. Both the main MUC and the ENC28J60 use the same clock. Netduino Mini has an 18.432MHz crystal. To use an ENC28J60, you'll want to either attach an ENC28J60 module with onboard crystal (recommended) or add the crystal circuitry. Chris

[hanzibal]

To create the oscillator, get a 25MHz HC-49S crystal and connect it between osc1 and osc2 with one load capacitor on each pin to ground as shown on page 5 in the datasheet. The crystal's datasheet will tell you what capacitor value to use. Crystals don't have polarity so you cant go wrong. You can almost certanly omit the series resistor. I believe this crystal will do fine:
http://www.ebay.com/...=item20c71074c7

...or you could get one of these cheap 5 USD ready made boards:
http://www.ebay.com/...=item2a2224ba7d

Either way, if you're looking to do tcp/ip, check out the miP stack:
http://forums.netdui...-netduino-mini/

Good luck!

[baxter]

I was able to get miP 0.3 running on a Mini with one of the ebay boards. It would stay on line for
several days and then for no apparent reason it would go down. To get things restarted, it was necessary
to repower and then redeploy miP. I have now turned my attention to a WIZ820io,

 

http://www.mouser.co...KDegoiLZuyo4ySA

[hanzibal]

Yeah, the W5200 has an integrated stack and would be much, much faster as well. Cost more though. @baxter: Please tell us if and when you got the Wiz up and running. I got a board similar to that and would be really nice if you could share some code for it. My board doesn't expose the !INT pin which seems really stupid. About your mIP project, wouldn't a software watchdog work, eg connecting a wire between !RST and an output pin and have that go low once a day or something like that?

[StefanUSMC]

I have a standalone ENC28J60 board for my testing, but will be deploying this and would like to get it all in one integrated solution. The series resistor was my biggest concern, but if that can be omitted the circuitry looks fairly simple.

 

Thanks for the help!

 

Brandon

[baxter]

@hanzibal,

I really haven't done much with this after an initial burst of enthusiasm. I concluded that miP 0.3 is still a work in progress which is why I moved to Wiznet. I then started to port some software to try to integrate with Chris Walker's experimental Wiznet drivers, but then I asked myself why do this if I have a Netduino Plus 2. I collected some references that might be of help to you; the most promising of which is,

 

http://tech.munts.co...Frameworks/ARM/

Look under directory, wiznet.

 

Other links,

http://blog.innovati...en-roberts.html

 

http://www.cashdolla...for-the-msp430/

 

http://www.ermicro.com/blog/?p=1773

 

http://code.google.c...er-w5200-driver

 

http://forums.parall...m-Post-3)/page2

 

http://blog.wiznet.c...by-ben-roberts/

 

http://www.tinyclr.c...er:2604&page=16

 

http://www.tinyclr.c...share/entry/187

 

Baxter

[hanzibal]

Thanks Baxter! Looks like I'm fully covered then. Actually, I was kinf of hoping you'd just serve me a ready baked cake :-)

[hanzibal]

The series resistor was my biggest concern, but if that can be omitted the circuitry looks...

There's a nice app note on designing oscillators at Microchip, should you run into problems:

http://ww1.microchip...otes/00949a.pdf