Monday, October 31, 2016

Starting RPi gpio output.



 Here is a little project I just started on. Have done a lot of work with a legacy Pc port. In fact, a lot of interfacing to different devices have been documented in my blogs. One thing you have to be careful of is that the pinouts vary between the different Raspberry Pi models.



Here is the wiring diagram for the original RPi and for the RPi zero. An article recommends 470 ohm resisters.




Not a fan of python, but there is a lot code that can be used.
Python code. (railroad track warning lights.)
--------------------
#Import libraries
import RPi.GPIO AS GPIO
import time

#set gpio numbering mode and defind pins
GPIO.setwarnings(False)
GPIO.setmode)GPIO.BOARD)
GPIO.setup(7, GPIO.OUT)
GPIO.setup(11, GPIO.OUT

#blink the leds
for x in range(0.10):
    GPIO output(7, True)
    GPIO output(11, False)
    time.sleep(.5)
    GPIO output(7, False)
    GPIO output(11, True)
    time.sleep(.5)

# cleanup the gpio pins before ending
GPIO output(11, False)
GPIO output(7, False)
GPIO.cleanup

Tuesday, October 11, 2016

Rpi zero composite out.



So you've got your Pi Zero, but you don't have an HDMI monitor! The Pi Zero has a composite video out port which is very easy to access, and we're going to show you how!  You'll need a few bits and pieces, including a soldering iron to solder some headers on:


We're going to be soldering two pin headers onto the Pi Zero, circled in red and labeled TV in the picture below



So, go ahead an solder your pin headers on! You can of course solder wires directly to the board if you'd like, but headers are neater (and their connection subsequently removable).



Now get your RCA connector, and plug the two male ends into the two screw terminals. Again, you can use wire for this, but male pins are probably neater.



Now we can plug the female end of the jumper wires into our Zero.
Polarity should always be "Positive" (+) of the RCA connector, to the pin labelled "TV" on the Raspberry Pi. In this case, it is our white jumper wire.



The Pi should automatically switch the output method depending on what you have plugged in, e.g. if you have no HDMI plugged in, and you connect the RCA, it should output via RCA. However, if you've pre-configured your system (for example on another Pi) it may not work.
If it doesn't work off the bat, you'll need to edit the Pi's config.txt file to force video output via RCA.
So, open up your Pi's config.txt file, you can do this in terminal using the command:
sudo nano /boot/config.txt
There are two lines you need to edit.
First, you need to REMOVE the comment # from the line
#sdtv_mode=2
So it should look like this:
sdtv_mode=2
Next, you need to ADD a comment # to the line
hdmi_force_hotplug=1
So it should look like this:
#hdmi_force_hotplug=1
Check the lines highlighted in red in the images below for clarification.

BEFORE



AFTER




Remember to save the config file when you exit!
That's it! You can now plug the Zero into your RCA/composite video and it should output on that channel!