Sending Voltage Signal from FPGA

[hussam95]

I want to send a TTL voltage signal from LabVIEW FPGA (NI 7856R Series) to a laser shutter and flipper to control them. How can I do that with this NI FPGA Module? I was reading some articles and comments, and some were saying about setting up a digital signal that will transfer to an output signal, but wasn't very clear. 

[wiebe@CARYA]

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@hussam95 wrote:

I want to send a TTL voltage signal from LabVIEW FPGA (NI 7856R Series) to a laser shutter and flipper to control them. How can I do that with this NI FPGA Module? I was reading some articles and comments, and some were saying about setting up a digital signal that will transfer to an output signal, but wasn't very clear. 

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How to you communicate to the shutter and flipper? Are the also TTL? Or serial? Or GPIB?, USB, TCP\IP? That is kind of critical...

[hussam95]

They are TTL Pulses. 

[wiebe@CARYA]

So make a loop that gets the input, do some logic and sets he outputs.

[JensG69]

BTW, the DIO-lines of a 7856R-card use LVTTL levels, i.e. high is 3.3 V, not 5 V as in TTL. So you either have to use an analog-out for a 5V signal or you have to look for some additional hardware that can convert the LVTTL to a TTL level.

Regards, Jens

[Minions]

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@jg69 wrote:

BTW, the DIO-lines of a 7856R-card use LVTTL levels, i.e. high is 3.3 V, not 5 V as in TTL. So you either have to use an analog-out for a 5V signal or you have to look for some additional hardware that can convert the LVTTL to a TTL level.

Regards, Jens

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TTL levels require an input above 2V for a logic high or an input below 0.8V for a logic low. Seeing that the 3.3V output of your FPGA is above the 2.0V level, a level shifter should not be required.

[wiebe@CARYA]

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@Minions wrote:

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@jg69 wrote:

BTW, the DIO-lines of a 7856R-card use LVTTL levels, i.e. high is 3.3 V, not 5 V as in TTL. So you either have to use an analog-out for a 5V signal or you have to look for some additional hardware that can convert the LVTTL to a TTL level.

Regards, Jens

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TTL levels require an input above 2V for a logic high or an input below 0.8V for a logic low. Seeing that the 3.3V output of your FPGA is above the 2.0V level, a level shifter should not be required.

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As I see it, 5V TTL might blow the input. 3.6 is max:

https://forum.allaboutcircuits.com/threads/cmos-and-lvttl-voltage-levels.62014/

Not sure if the 7856R can take more, but if it's spec'd at LVTTL, it's not required to.

Two resistors will fix that. Still inconvenient, depending on the situation...

[Minions]

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wiebe@CARYA wrote:

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@Minions wrote:

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@jg69 wrote:

BTW, the DIO-lines of a 7856R-card use LVTTL levels, i.e. high is 3.3 V, not 5 V as in TTL. So you either have to use an analog-out for a 5V signal or you have to look for some additional hardware that can convert the LVTTL to a TTL level.

Regards, Jens

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TTL levels require an input above 2V for a logic high or an input below 0.8V for a logic low. Seeing that the 3.3V output of your FPGA is above the 2.0V level, a level shifter should not be required.

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As I see it, 5V TTL might blow the input. 3.6 is max:

https://forum.allaboutcircuits.com/threads/cmos-and-lvttl-voltage-levels.62014/

Not sure if the 7856R can take more, but if it's spec'd at LVTTL, it's not required to.

Two resistors will fix that. Still inconvenient, depending on the situation...

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This is all a non-issue as long as the FPGA is being used as an output to control the external equipment as stated in the original entry.    If the FPGA is used for monitoring any responses or inputs, then this may change.

[wiebe@CARYA]

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@Minions wrote:

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wiebe@CARYA wrote:

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@Minions wrote:

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@jg69 wrote:

BTW, the DIO-lines of a 7856R-card use LVTTL levels, i.e. high is 3.3 V, not 5 V as in TTL. So you either have to use an analog-out for a 5V signal or you have to look for some additional hardware that can convert the LVTTL to a TTL level.

Regards, Jens

---

TTL levels require an input above 2V for a logic high or an input below 0.8V for a logic low. Seeing that the 3.3V output of your FPGA is above the 2.0V level, a level shifter should not be required.

---

As I see it, 5V TTL might blow the input. 3.6 is max:

https://forum.allaboutcircuits.com/threads/cmos-and-lvttl-voltage-levels.62014/

Not sure if the 7856R can take more, but if it's spec'd at LVTTL, it's not required to.

Two resistors will fix that. Still inconvenient, depending on the situation...

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This is all a non-issue as long as the FPGA is being used as an output to control the external equipment as stated in the original entry.    If the FPGA is used for monitoring any responses or inputs, then this may change.

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In the OP In my head there is was an input.

[hussam95]

Thank you all for the comments. I am using the FPGA DIO line to send a signal to a shutter to open/close. I shouldn't be needing a level shifter for that one? I connected a DIO (Output) to a switch that turns on/off, but my shutter doesn't move.