pi_status

Add I2C SD1306 Display and Lighted Momentary Push-button to Raspberry Pi

More information is available at https://teelsys.com/2022/10/16/raspberry-pi-4-19-rack-with-four-units/

The inspiration for this project is from a UCTRONICS Pi Rack that Jeff Geerling reviewed on his YouTube channel. The UTRONICS product may be seen at https://www.uctronics.com/cluster-and-rack-mount/for-raspberry-pi/1u-rack-mount/uctronics-pi-rack-pro-for-raspberry-pi-4b-19-1u-rack-mount-support-for-4-2-5-ssds.html.

Materials

SD1306 128x64 pixel display
Lighted momentary switch (Normally Open (NO))
220 Ohm Resistor
Raspberry Pi 4

Wiring

Item	Physical Pin	GPIO/Function	Note
Display VCC	1	3v3
Display SDA	3	2 (SDA)
Display SCL	5	3 (SCL)
Display GND	6	GND
Switch	7	4	Pulled High
Switch	9	GND
LED+	13	27	220 Ohm Resistor in Series
LED-	14	GND

Installation

NOTES:

The following steps make are run with the pi user account in the home directory. If running as a different user or location other than /home/pi, you will need to adjust the paths used in this document.
The instructions below are for verbose logging, which may result in large files that may cause the disk space to fill up and/or cause excessive writes. If this behavior is not desired, remove the "-v" flag from the launcher.sh file.
To capture all errors and output, with or without logging turned on, you may change the line in crontab to "sh /home/pi/pi_status/display/launcher.sh 2>>/home/pi/pi_status/display/logs/cron_err.txt 1>/home/pi/pi_status/display/logs/cron_log.txt"

Installation Steps

Install Required Libraries (See https://learn.adafruit.com/monochrome-oled-breakouts/python-setup)
- sudo pip3 install adafruit-blinka
- sudo pip3 install adafruit-circuitpython-ssd1306
Clone the files from GitHub
- git clone https://github.com/richteel/pi_status.git
Run the script on reboot
- sudo crontab -e
- Add the following line to the end of the file
  @reboot sh /home/pi/pi_status/display/launcher.sh
Run the statement in the crontab to make certain that all is fine
- sh /home/pi/pi_status/display/launcher.sh
Reboot to see if all is working as expected
- sudo reboot now

Notes on the Running Script

You may want to stop the script or view the output of the script. First you will need to know the PID of the running script. Run the following to find the PID

ps ax | grep 'code.py' | grep -v grep

You will see output similar to the following

pi@pi-four:~ $ ps ax | grep 'code.py' | grep -v grep
 403 ?        R     17:35 python3 /home/pi/pi_status/display/code.py

From the output, we see that the PID is 403. We may now stop the script using the following command.

sudo kill 403

We can view the error output by using the tail command.

sudo tail -f /proc/403/fd/2

or
sudo tail -f /home/pi/pi_status/display/logs/error.txt

We can view the standard output by using the tail command.

sudo tail -f /proc/403/fd/1

or
sudo tail -f /home/pi/pi_status/display/logs/detail.txt

We can view the verbose output by using the tail command.

sudo tail -f /home/pi/pi_status/display/logs/detail.txt

NOTE: Use CTRL + C to exit from the tail command.

You may start the script again by running the following command.

sh /home/pi/pi_status/display/launcher.sh -v &

pi@pi-four:~ $ sh /home/pi/pi_status/display/launcher.sh -v &
[2] 1974
[1]   Exit 1                  sh /home/pi/pi_status/display/launcher.sh 2>> /home/pi/pi_status/display/logs/cron_err.txt > /home/pi/pi_status/display/logs/cron_log.txt
pi@pi-four:~ $ 2022-10-10 18:46:17      Starting Pi Status
2022-10-10 18:46:17     Starting Pi Status
2022-10-10 18:46:17     Logging = True
2022-10-10 18:46:17     Logging Verbose = True
2022-10-10 18:46:17     Pi Status       Version 0.2     -1

sh /home/pi/pi_status/display/launcher.sh 2>>/home/pi/pi_status/display/logs/cron_err.txt 1>/home/pi/pi_status/display/logs/cron_log.txt &

pi@pi-four:~ $ sh /home/pi/pi_status/display/launcher.sh 2>>/home/pi/pi_status/display/logs/cron_err.txt 1>/home/pi/pi_status/display/logs/cron_log.txt &
[1] 1931
pi@pi-four:~ $

Operation

The script addresses a few requirements for providing system status, script status, and shutting down of the Raspberry Pi. There are optional parameters to control logging. Logs are written to the the logs directory within the script folder. Default location if installed in the pi user's home directory is /home/pi/pi_status/display/logs.

-h Display help

pi@pi-four:~ $ python3 /home/pi/pi_status/display/code.py -h
usage: code.py [-h] [-l] [-v]

Raspberry Pi Status Monitor

optional arguments:
  -h, --help  show this help message and exit
  -l          Turn on basic logging
  -v          Allow verbose logging of status data to a file
pi@pi-four:~ $

-l Default Logging
- Writes stdout to /home/pi/pi_status/display/logs/status.txt
  - Messages such as start, end, startup parameters, and information shown on OLED display
- Writes stderr to /home/pi/pi_status/display/logs/error.txt
  - Start and end messages as well as trapped errors
  - Will not capture error messages resulting in a crash. To capture errors from a crash, it is necessary to redirect stderr to a file by executing the script with a redirection such as code.py 2>errors.log
- Information from the display is logged as
  - Line 1 (IP Address)
  - Line 2 (Title)
  - Line 3 (Value)
  - Line 4 (Number of blocks to shade from 0 to 10. The value -1 indicates not to show the blocks.)
-v Verbose Logging (Includes Default Logging plus Details)
- When using the verbose option, there is no need for the logging option as the verbose option turns on the default logging option
- Writes to /home/pi/pi_status/display/logs/detail.txt
- Produces a tab delimited file that may be imported into a spreadsheet or database
- Contains all data from each update at a rate of once every 10 seconds.
  - Date and Time (local)
  - Host Name
  - IP Address
  - IP Ethernet
  - IP Wi-Fi
  - CPU Temperature
  - Memory Total
  - Memory Free
  - Memory Used
  - Memory Percent
  - Disk Total
  - Disk Used
  - Disk Free
  - Disk Percent
  - CPU Usage Percent 1 min
  - CPU Usage Percent 5 min
  - CPU Usage Percent 15 min

Screens

There are a few screens to provide system information. The screens are shown for 10 seconds each. Once the last screen is shown, the first screen is shown. The system information is refreshed before each screen is shown but is not updated while being displayed.

Splash screen: Shown once to display software version information
NAME: Displays the hostname of the Raspberry Pi
RAM: Shows the total memory as well as the percentage of memory in use
TEMP: Shows the CPU Temperature in degrees Celsius (NOTE: The scale shows the temperature between the operational limits of the Raspberry Pi, with the low end bring -40 C and the high end being 85 C)
DISK: Shows the total disk space in GB and the percentage of disk space in use
CPU: Shows the average percent load of the CPU over the last minute

Switch

Pressing and holding the switch for 10 seconds will cause the Raspberry Pi to shutdown safely by issuing the shutdown command to the system.

LED

The LED in the lighted switch will be lit when the script is running. If there is a delay from issuing the shutdown command and the script exiting, the LED will flash once every second. It is unlikely that you will see the LED flashing unless the operating system is busy with other tasks before signaling the script to terminate.

NOTE: The screen and the switch's LED will turn off when the script ends.

Troubleshooting

Here are some things to try to determine what may be an issue if the display or script fails.

Display not working and "ValueError: No I2C device at address: 0x3c" is shown in the cron_erros.txt log file
- Open a terminal and type the following command:
  i2cdetect -y 1
  
  If you see the following output, check your wiring to the display as the display was not found on the I2C bus.

pi@pi-four:~ $ i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
pi@pi-four:~ $

The expected output is the following showing a device was detected at address 3c,

pi@pi-four:~ $ i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- 3c -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
pi@pi-four:~ $

More troubleshooting tips are available at https://teelsys.com/2022/10/16/raspberry-pi-4-19-rack-with-four-units/.

richteel/pi_status