AnalogIn.Read() (and how it relates to sensors)

[mhectorgato]

I was thinking of getting an Ultrasonic Maxbotix LV-EV sensor.

LV-MaxSonar-EZ_Datasheet.pdf

Looks like this would connect in similar fashion to the Sharp IRs do to a FEZ - using an analog pin, and the corresponding AnalogIn object in NETMF.

The question I have is this: How is the sensor reading started? Meaning:

(1) Are these sensors always running? So that when you do a AnalogIn.Read() and it just returns the last value.

Or

(2) When you do a Read(), it sends a signal (that’s abstracted by NETMF/GHI) to the device, that starts the sensor reading process (in this case generate a sound wave and process the results)?

Thanks

[EriSan500_Eric]

From the first lines of the datasheet:

[quote]The
interface output formats included are pulse
width output, analog voltage output, and
serial digital output.[/quote]

When you use the analog voltage output, you can just do AnalogIn.Read()

[mhectorgato]

Right … that much I get:

Outputs analog voltage with a scaling factor of (Vcc/512) per inch. A supply of 5V yields ~9.8mV/in. and 3.3V yields ~6.4mV/in. The output

What I was wondering is this:
Does the Read() “trigger” something in the sensor to start it’s process?

For example this ultrasonic - is it continally generating it’s sound wave and processing the result as long as it’s receiving power? Then when do a Read() it just returns the last result?

Or is it sitting domant, when you issue the Read() it at point generates the wave, processes the result, and then go back to “sleep”, waiting for the next request?

[EriSan500_Eric]

your answer is this:

For example this ultrasonic - is it continally generating it’s sound wave and processing the result as long as it’s receiving power? Then when do a Read() it just returns the last result?