Author Topic: FPGA outputs  (Read 3353 times)

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Offline mosulllTopic starter

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FPGA outputs
« on: March 30, 2008, 07:40:33 AM »
hello. My friend and I are trying to build our first robot. We are trying to use instead of a microcontroller a FPGA, a spartan 3 . I was wondering how we could use, and if of course , the FPGA to put out the signals necessary to command our servos. I tried to use the expansion connectors but after programming the output.. all the pins have the same voltage , even though i tried to make at least some outputs to have a "0" level.
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Offline Rebelgium

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Re: FPGA outputs
« Reply #1 on: March 30, 2008, 08:12:37 AM »
you'll need to program PWM to the outputs used for servo's.
But ofcourse first you'll have to find what's wrong now...
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Offline Kohanbash

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Re: FPGA outputs
« Reply #2 on: March 30, 2008, 11:15:31 PM »
When you synthesize the chip are you selecting which pins should be Input and Output
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Offline mosulllTopic starter

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Re: FPGA outputs
« Reply #3 on: March 31, 2008, 05:53:22 AM »
Yes, I have selected the pins. I hope I did it right. I've read the user guide, and I think I've chosen the right ones. Though, I still have several questions. On my FPGA there are 3 Expansion Connectors, each one having 40 pins. Pin 1 should be the GROUND and pin 3 should be Vcc (+3.3V) and the other ones should be programmable (I guess...). If I measure the voltage between the PIN3 (+3.3V) and PIN1 (ground), I obtain -0,77 V.. If I measure the voltage between PIN3 (+3.3V) and the ground from the DC adapter, I obtain +2,5 V. My question is what will the voltage for controlling the servo be? I know it might be a very stupid question, but I don't get it...
I'd appreciate if you could tell me where I could find some information about programming the expansion connector.
Thank you.
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Offline Admin

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Re: FPGA outputs
« Reply #4 on: April 06, 2008, 12:46:32 PM »
Quote
My friend and I are trying to build our first robot.
You should probably stick to the simpler stuff, like a microcontroller . . .

Quote
My question is what will the voltage for controlling the servo be? I know it might be a very stupid question, but I don't get it...
5V (3.3V may work, but will result in potential issues)
http://www.societyofrobots.com/actuators_servos.shtml

Quote
Pin 1 should be the GROUND and pin 3 should be Vcc (+3.3V) and the other ones should be programmable (I guess...). If I measure the voltage between the PIN3 (+3.3V) and PIN1 (ground), I obtain -0,77 V.. If I measure the voltage between PIN3 (+3.3V) and the ground from the DC adapter, I obtain +2,5 V.
It sounds like your grounds are set as common . . .
http://www.societyofrobots.com/robot_faq.shtml#circuit_debug
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