Raspberry Pi Forums

Posted: **Sun Dec 23, 2012 2:18 am**

Ok, so this is my very first Rpi project, I'm trying to hook up a ePIR from sparkfun.

Pins 1,3,4 and 8 are all GND.
Pins 2,6 are 3.3v.
Pin 5 is GPIO18.
Pin 7 is GPIO17.

http://www.sparkfun.com/datasheets/Sens ... PS0284.pdf

I was trying to adapt this:
http://ninjablocks.com/groups/raspberry ... ir-sensor/

Now, what happens when I run the script is it just says "No Motion." over and over.

As I was looking over the spec I thought maybe it was because Pin 6 in his guide is set to 3.3v, but if you look at the spec sheet it says GND-1.0v means MDT will go active when motion is detected and setting it to Vdd prevents MDT from going active. However jumping Pin 6 to GND did...nothing.

The only real troubleshooting I know how to do is to see what happens when I disconnect the device, at which point the script says False instead of True but past that I don't really know how else to troubleshoot it. Any ideas?

Code: Select all

GPIO.setup(17, GPIO.OUT)
GPIO.setup(18, GPIO.IN)
GPIO.output(17, GPIO.HIGH)

input_value = GPIO.input(18)
print(input_value)
while 1:
        if GPIO.input(17):
                print('No Motion.')
        else:
                print('Motion?')
        sleep(2)
GPIO.cleanup()

Posted: **Sun Dec 23, 2012 10:32 am**

It seems to default to serial link mode. Have you tried using the serial link to communicate with the device?

Posted: **Sun Dec 23, 2012 4:39 pm**

Hardware Interface Mode Selection
The Hardware Interface Mode is selected when TXD/SNS is between 0 V and 1.8 V
during power ON or when exiting SLEEP Mode.

TXD/SNS is set to ground so, that should be setting it to HWI correct?

I have not tried connecting in serial, they described it as more advanced so I figured for my first time I'd use the "easy" way lol. I'll look into serial mode, but ultimately I would still like to figure out how to use it in HWI.

Posted: **Sun Dec 23, 2012 4:41 pm**

Also, am I wrong to think that just running a lead from the 0.0v pin on the Rpi would set it to 0v? This is a terrible time for my stupid multimeter to flake out. But they make no mention of pin 4 being driven at all so again, hooking it up to nothing should be the same as setting it to ground yeah? Air is going to be 0.0v.

Note I have no resistors at all in this mix as it takes 3.3 so thats fine, and everything else is set to ground or GPIO.

Thanks for the input!

Posted: **Sun Dec 23, 2012 4:57 pm**

Thanks when I try to hook it up in serial I will bear that in mind! I do think I'm going to try a bit longer to get it to work in HWI over the GPIO, partially because, well, I want to figure out how to work with GPIO, but also because it just seems more suitable for what I'm using it for.

Thanks!

Posted: **Sun Dec 23, 2012 8:26 pm**

Ok, I figured it out.

First, the code (as that was the real problem).

from time import sleep
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)

GPIO.setup(25, GPIO.OUT)
GPIO.setup(24, GPIO.IN)

GPIO.output(25, True)
sleep(3)
while 1:
input_value = GPIO.input(24)
print(input_value)
sleep(1)
GPIO.cleanup()

I set Pin 6 back to VDD (3.3v) and now when I run that script it properly changes from true to false (and back) based on motion detection!

Awesome! I know this is probably basic as heck old hat to you guys but this is now my first working example of GPIO, with something I couldn't find any plug and play code for, so I'm pretty pleased right now.

Thanks so much for the input guys, you got me thinking laterally and that was crucial, really appreciate it!

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