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Pulse Width Measurement in C
8 years 2 months ago #29530012
by beerbot
Pulse Width Measurement in C was created by beerbot
Having set an input to pulse mode (with the PC Utility or ^PMOD ?), I want to
then read the pulse width in my C program. RioReadPulseAnaInputs() is a "short."
How do I use that short as a pulse width measurement? Is it simply the width in microseconds?
Given that there is a millisecond or two delay in updating a pin's value, will the
pulse value be the width of the last pulse before the update, the average since the last update, or ...?
then read the pulse width in my C program. RioReadPulseAnaInputs() is a "short."
How do I use that short as a pulse width measurement? Is it simply the width in microseconds?
Given that there is a millisecond or two delay in updating a pin's value, will the
pulse value be the width of the last pulse before the update, the average since the last update, or ...?
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8 years 2 months ago #29530013
by TechSupport
Replied by TechSupport on topic Pulse Width Measurement in C
What exactly is this "short" it is reading? Is it a 0uS reading or something else I am not aware of?
To read back the pulse input, you can send a query of ?pi.
?pi 1 should query back the Pulse input 1 value.
To read back the pulse input, you can send a query of ?pi.
?pi 1 should query back the Pulse input 1 value.
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8 years 2 months ago #29530016
by beerbot
Replied by beerbot on topic Pulse Width Measurement in C
"short" is the C language data type that you define in the Datasheet C Library Functions for this read.
That is, you define the function RioReadPulseAnaInput() as a data type "short" (page 14, first function).
Since you don't use the modifier "unsigned," this means that the value returned by that function is a signed integer, likely 16 bits in size.
The question is, when the pin is set to "Pulse Input Mode" (^PMOD), what does the returned value represent?
For example, it could be the pulse width in microseconds or in Hz. Your "Power Stage Electrical Specifications" on page 9 of the Datasheet shows both duration and frequency values for pulse parameters.
I assume that when the pin is set to analog input mode the value represents the voltage in millivolts?
I want to use the C Library, not the console/basic commands, but the same question applies for ?pi 1. That is, what data is returned?
That is, you define the function RioReadPulseAnaInput() as a data type "short" (page 14, first function).
Since you don't use the modifier "unsigned," this means that the value returned by that function is a signed integer, likely 16 bits in size.
The question is, when the pin is set to "Pulse Input Mode" (^PMOD), what does the returned value represent?
For example, it could be the pulse width in microseconds or in Hz. Your "Power Stage Electrical Specifications" on page 9 of the Datasheet shows both duration and frequency values for pulse parameters.
I assume that when the pin is set to analog input mode the value represents the voltage in millivolts?
I want to use the C Library, not the console/basic commands, but the same question applies for ?pi 1. That is, what data is returned?
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8 years 2 months ago - 8 years 2 months ago #29530017
by TechSupport
Replied by TechSupport on topic Pulse Width Measurement in C
Thanks for clarifying. I don't have any knowledge of the C language programming.
^pmod means that you are changing the pulse mode parameter for an input. If you are broadcasting to all inputs on the pulse, then 0 is used.
To change a pulse/analog input 1 from analog raw to pulse raw, then it can be done via a serial command which is ^pmod 1 2.
If you were to query the actual state of pmod 1, you would send ~pmod 1.
I've attached a screenshot using Robonav.
I queries the pmod to see what the states were.
Then I changed input 1 to become pulse raw.
Then I queried again to see that the change took effect, where position 1 went from 0 to a 2.
^pmod means that you are changing the pulse mode parameter for an input. If you are broadcasting to all inputs on the pulse, then 0 is used.
To change a pulse/analog input 1 from analog raw to pulse raw, then it can be done via a serial command which is ^pmod 1 2.
If you were to query the actual state of pmod 1, you would send ~pmod 1.
I've attached a screenshot using Robonav.
I queries the pmod to see what the states were.
Then I changed input 1 to become pulse raw.
Then I queried again to see that the change took effect, where position 1 went from 0 to a 2.
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