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Altera_Forum
Honored Contributor I
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Interfacing with Max V Development Board

I just acquired a Max V Development board to learn programming on CPLDs. I've already made some headway and have managed to utilize the push buttons and LEDs. I was thinking of utilizing the GPIO headers to interface with a AVR Mega 168. My question is, how can I supply power to the AVR from the board? 

 

The GPIO header lists a 3.3V source and an external connecter on the board is provided. However, if I do attach a 3.3V source here - what about the ground? Is the ground connected elsewhere in the system? If not, how do I provide a common reference to both the AVR and the development board? 

 

My limited knowledge makes me think that I'm supposed to connect a 3.3V voltage regulator to the 3.3V CONN and GND ports. Will this allow me to power the AVR without problems?
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4 Replies
Altera_Forum
Honored Contributor I
66 Views

 

--- Quote Start ---  

I just acquired a Max V Development board to learn programming on CPLDs. I've already made some headway and have managed to utilize the push buttons and LEDs. I was thinking of utilizing the GPIO headers to interface with a AVR Mega 168. My question is, how can I supply power to the AVR from the board? 

 

--- Quote End ---  

 

 

You should be able to power the AVR board and CPLD boards independently, eg. from their respective USB connectors (if that is how they are normally powered).  

 

All you really need to do is to connect the signals on the GPIOs on the respective boards, and connect a few ground pins. 

 

The ground pins establish the common reference, and provide a path for return currents. You might be able to get away without the ground, if both boards are being powered from a single computer, however, its would be a good idea to connect grounds on the respective GPIO connectors. 

 

Cheers, 

Dave
Altera_Forum
Honored Contributor I
66 Views

 

--- Quote Start ---  

You should be able to power the AVR board and CPLD boards independently, eg. from their respective USB connectors (if that is how they are normally powered).  

 

All you really need to do is to connect the signals on the GPIOs on the respective boards, and connect a few ground pins. 

 

The ground pins establish the common reference, and provide a path for return currents. You might be able to get away without the ground, if both boards are being powered from a single computer, however, its would be a good idea to connect grounds on the respective GPIO connectors. 

 

Cheers, 

Dave 

--- Quote End ---  

 

 

Thank you very much for a quick response! I don't have a AVR board, just a AVR Mega 168 sitting on a breadboard for prototyping purposes. I can power it up with a 3.3V source from a LM317. 

 

Now, all I have to do is connect the ground of the LM317 to the GND pad on the development board? This will provide a common reference point and I ought to be ready to go. 

 

Am I correct in my understanding?
Altera_Forum
Honored Contributor I
66 Views

 

--- Quote Start ---  

Thank you very much for a quick response! I don't have a AVR board, just a AVR Mega 168 sitting on a breadboard for prototyping purposes. I can power it up with a 3.3V source from a LM317. 

 

Now, all I have to do is connect the ground of the LM317 to the GND pad on the development board? This will provide a common reference point and I ought to be ready to go. 

 

Am I correct in my understanding? 

--- Quote End ---  

Yes, that sounds correct. 

 

Cheers, 

Dave
Altera_Forum
Honored Contributor I
66 Views

For fast digital signals, you would always want to connect as much ground pins as available along with the signal, no matter if there's a common ground connected elsewhere. If you don't connect the grounds directly with the signals, you are radiating fast edges of the return currents all around your enviroment and pick up interferences as well.

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