Featured Articles
Announcing Pi
Technical Specifications
Raspberry Pi FAQs
Win a Pi
GPIO Pinout
Raspberry Pi Wishlist
Comparison Chart
Quiz
Group Actions
Engagement
  • Author Author: fustini
  • Date Created: Date Created
  • Views 2786 views
  • Likes 1 like
  • Comments 10 comments
Related
Recommended

Display tweets on a character LCD

fustini
imageWant to build this project?
View Parts

 

image

I followed Adafruit's great Drive a 16x2 LCD with the Raspberry Pi tutorial using:

 

However, identified a problem with the Adafruit_CharLCD library for the Rev 2.0 Pi as GPIO 21 and 27 have changed.  It turned out the simplest fix is to switch the pin numbering scheme to that of the physical header rather than the Broadcom SoC.  Until Adafruit accepts my pull request, I'd recommend using Adafruit_CharLCD from my repository if you have a Rev 2.0 Pi.

 

After sorting that out, I wrote a Python script to display tweets for a given hashtag (display-hashtag.py) which can be found in my tweetypi GitHub repo.  I use Python Twitter Tools by Mike Verdone to search Twitter.

 

Follow these instructions to install the hashtag display:

pi@raspberrypi ~ $ sudo pip install twitter

 

pi@raspberrypi ~ $ mkdir python

 

pi@raspberrypi ~ $ cd python

 

pi@raspberrypi ~/python $ git clone https://github.com/pdp7/Adafruit-Raspberry-Pi-Python-Code.git

Cloning into 'Adafruit-Raspberry-Pi-Python-Code'...

remote: Counting objects: 185, done.

remote: Compressing objects: 100% (117/117), done.

remote: Total 185 (delta 83), reused 158 (delta 56)

Receiving objects: 100% (185/185), 55.25 KiB, done.

Resolving deltas: 100% (83/83), done.

 

pi@raspberrypi ~/python $ git clone https://github.com/pdp7/tweetypi.git

Cloning into 'tweetypi'...

remote: Counting objects: 13, done.

remote: Compressing objects: 100% (10/10), done.

remote: Total 13 (delta 2), reused 8 (delta 2)

Unpacking objects: 100% (13/13), done.

 

pi@raspberrypi ~/python $ cd tweetypi

The only required argument for display-hashtag is the hashtag. The usual '#' hashtag prefix should be omitted from the argument as it is added by the Python code. The defaults assume 16x2 char LCD:

sudo ./display-hashtag bears

Here's a video clip of it running:

 

 

The HashTagDisplay class supports character LCD from 16x1 up to 20x4.  Here would be the arguments for 20x4 LCD:

sudo ./display-hashtag --verbose --cols 20 --rows 4 --delay 3 bears

 

image

Video clip of 20x4 display:

 

 

Cheers,

Drew

 

 

element14
Product Name*DescriptionBuy All Parts
Raspberry Pi Model B with SD Card Raspberry Pi model B and 8GB SD Card with NOOBS preinstalled
Optical Mouse Basic USB optical mouse
Raspberry Pi Power Supply 120-240v to 5V power supply with micro USB connector
Keyboard Basic USB keyboard
16x2 character LCD 16x2 character monochrome LCD
10k trimmer potentiometer 10k ohm, single turn trimmer potentiometer
Adafruit Pi Cobbler GPIO breakout kit for Raspberry Pi
Breadboard Basic breadboard with 830 connection points
Jumper wire bundle Jumper wires for use on breadboard

 

*Products and resources listed are listed to help members build their own Pi Projects. They are suggestions and listed for educational purposes. For substitutions of any parts, please post a question asking the original author.

  • I have not looked at your code in detail, is there ever an instance where pin 5 on the LCD could be pulled high? This is where I would be concerned. I agree that you would be 100% safe as long as LCD pin 5 was never pulled high (this changes the data direction).

  • in reply to Former Member

    Hi - yeah, the 5V LCD and the 3.3V I/O Pi seemed strange at first, but as the Adafruit tutorial explained, the Pi pins are only output mode to the LCD.  3.3V is ok for a High with 5V LCD.  There is no 5V coming back to the Pi pins from the LCD.  I suppose there is the potential for a problem if one makes a wiring mistake.  A logic level converter would be the safest way but does add cost and complexity.

     

    I think you are right regarding the pot.  Adafruit includes 10k pot I see with their LCDs.  I think I was having trouble finding something bigger than 1k from Newark that had a knob on it.

     

    P.S. how depressing to revisit this post where my LCD displays the Bears record of 8-3, before they promptley fell off a cliff.  oy, someday I'm going to give up on football and save myself the time, money, and frustation image

  • I have noticed that you have specified a 1k potentiometer in your parts list. However, upon reading the datasheet for the LCD, a 10k to 20k pot is recommended. Just thought I would make you aware of this. Also, have you ever had any issues when reading from the LCD since the LCD you have specified uses 5V logic levels and the GPIO pins on the Pi are not 5v tolerant?

     

    Nash Kaminski

  • in reply to Former Member

    Hi, I can't seem to replicate that even with a new user on my linux system (so it wouldn't have anything auth settings cached): 

     

    gittest@lappy486:~$ git clone https://github.com/pdp7/tweetypi.git

    Cloning into 'tweetypi'...

    remote: Counting objects: 100, done.

    remote: Compressing objects: 100% (78/78), done.

    remote: Total 100 (delta 54), reused 48 (delta 16)

    Receiving objects: 100% (100/100), 18.47 KiB, done.

    Resolving deltas: 100% (54/54), done

     

    You could try the git protocol instead of http with this command:  

     

    git clone git://github.com/pdp7/tweetypi.git 

     

    It's read only so I wouldn't imagine there would be a un/pw needed.  You can also download the files as a zip with:  https://github.com/pdp7/tweetypi/archive/master.zip

  • Hi Drew,

    It's asking me for a user/password when I :

    git clone https://github.com/pdp7/tweetypi.git

    What am I doing wrong or ??

     

    Ta Neil