Need advice for creating nS time delay

[Ioannis]

Although I have not made anything on FPGA's I see them now as an approrpiate solution.

They can be really fast!

Now about the device, I could not find a detailed pdf. Only a 2-page short datasheet. Do you have a complete copy? From the short one I think it is not as fast as you have stated.

Ioannis

[sayzer]

Although I have not made anything on FPGA's I see them now as an approrpiate solution.

They can be really fast!

Now about the device, I could not find a detailed pdf. Only a 2-page short datasheet. Do you have a complete copy? From the short one I think it is not as fast as you have stated.

Ioannis

Here are the detailed data sheets.

Unfortunately, application note file is 224KB, forum limit is 200KB.

[Acetronics2]

Hi, Sayzer

Hmmmm, 10 µm center bandpass ... that's a human motion detector !!!

Did you ask for the application Kit from Perkin-Elmer ???

http://optoelectronics.perkinelmer.c...pyroappkit.pdf


By the way ...

having a closer look to your datasheet ... it appears ( to me ... LOL )

1) you must wait for the sensor's output HIGH level ( PIC as input : Hi Z state ...)

2) When pic ready, generate a LOW 200ns MINIMUM pulse, then a HIGH 200 ns MINIMUM pulse

3) Pic as Input for 1µS MINIMUM ( Hi - Z ! ) then reads level


4) generate 200ns MINI low pulse , then 200 ns MINI high pulse ... etc, etc : we're back to step 2)

that repeated for the 15 bits ...

No "hyper high speed" processor required here as 200ns and 1µs are MINIMA ... ( the data is read at the speed given by the low to high transitions sent by the processor

so, try 24µs instead of 200ns and 24µS instead of 1µs waiting ... ( it's the pauseus minimum @ 4 Mhz ...)
after that you will be able to speed it up a bit using @nop !!!




Alain

[sayzer]

Hi, Sayzer

Hmmmm, 10 µm center bandpass ... that's a human motion detector !!!

Did you ask for the application Kit from Perkin-Elmer ???

http://optoelectronics.perkinelmer.c...pyroappkit.pdf

Alain

When I run the circuit on F877 with 20Mhz, I get very good results.
So I have no problem with the circuit; communication etc.

[Acetronics2]

Haaaaaa,

good news !!! you've got it working ...

now, from the datasheet it appears the sensor outputs a new "ready" signal every 2.84 ms ...

do you use polling or interrupting to initiate your reading sequence ???

Alain

[sayzer]

Alain,

I already got it working weeks ago.

The issue is that I need to make it work at 4Mhz.

For new sampling, I am giving it more then it needs. (it needs 3.7mS, I give it 10mS).

BTW; I added Application note; sampling example to my post above.

[Ioannis]

Hi Sayzer.

As Alain said and after looking at the datasheets, there is no need for hyper speed controller. What the DS states, are the minimum pulse width that you are allowed to apply. So, in case you have an extra-super-duper-high-speed controller capable to output 1ps pulses the sensor won't be able to follow.

You can just apply the pulses as fast as possible for the unique reason, to get your data soon. Otherwise there is no need to hurry.

As I understood the procedure:

1. MCU applies a high pulse for at least 200ns

2. MCU enter Z-state and sensor understands that MCU will read now the data

3. Sensor outputs the data bit

4. MCU reads the data bit

5. MCU outputs new high pulse

etc...

All you have to do is repeat the cycle as fast as possible if you want "real time" surveilance.

Ioannis


Ioannis