Corning Community College
CSCS1730 UNIX/Linux Fundamentals
To create a set of scripts that operate the sequence of LEDs located on the raspberry pi + breadboard setups located at each pod table.
In a group, you will be creating:
At each pod table is a dedicated raspberry pi 1 model B, interfaced with a breadboard and an array of eight LEDs, each wired up individually to a Raspberry Pi general purpose I/O pin.
Using the 'WiringPi' interface (a software library that also provides some command-line commands, such as the gpio tool), we can interact with these I/O pins for purposes of input and output.
Locating the appropriate pi (the one situated at your table), you will want to ssh into it from a pod or lab46 terminal.
There are four of these systems, numbered as follows:
Each pi is equipped with a standard raspbian release of Linux (one of the default distributions for the raspberry pi), default user credentials unchanged, so to access we have:
You will need to ssh into the geographically appropriate pi (shared by your group)
lab46:~$ ssh pi@pi1b_0X
NOTE that, just like the first time you accessed lab46, you will likely be prompted to approve the connection (“authenticity of host cannot be established” message) by answering the full “yes” and hitting enter, before being prompted for the password.
Using the gpio tool on the pi in question, we can obtain the current status of the GPIO pins on the pi with the readall parameter; output will appear as follows:
pi@pi1b_0#:~ $ gpio readall +-----+-----+---------+------+---+-Model B1-+---+------+---------+-----+-----+ | BCM | wPi | Name | Mode | V | Physical | V | Mode | Name | wPi | BCM | +-----+-----+---------+------+---+----++----+---+------+---------+-----+-----+ | | | 3.3v | | | 1 || 2 | | | 5v | | | | 2 | 8 | SDA.1 | IN | 1 | 3 || 4 | | | 5v | | | | 3 | 9 | SCL.1 | IN | 1 | 5 || 6 | | | 0v | | | | 4 | 7 | GPIO. 7 | IN | 1 | 7 || 8 | 1 | ALT0 | TxD | 15 | 14 | | | | 0v | | | 9 || 10 | 1 | ALT0 | RxD | 16 | 15 | | 17 | 0 | GPIO. 0 | IN | 0 | 11 || 12 | 0 | IN | GPIO. 1 | 1 | 18 | | 27 | 2 | GPIO. 2 | IN | 0 | 13 || 14 | | | 0v | | | | 22 | 3 | GPIO. 3 | IN | 0 | 15 || 16 | 0 | IN | GPIO. 4 | 4 | 23 | | | | 3.3v | | | 17 || 18 | 0 | IN | GPIO. 5 | 5 | 24 | | 10 | 12 | MOSI | IN | 0 | 19 || 20 | | | 0v | | | | 9 | 13 | MISO | IN | 0 | 21 || 22 | 0 | IN | GPIO. 6 | 6 | 25 | | 11 | 14 | SCLK | IN | 0 | 23 || 24 | 1 | IN | CE0 | 10 | 8 | | | | 0v | | | 25 || 26 | 1 | IN | CE1 | 11 | 7 | +-----+-----+---------+------+---+----++----+---+------+---------+-----+-----+ | BCM | wPi | Name | Mode | V | Physical | V | Mode | Name | wPi | BCM | +-----+-----+---------+------+---+-Model B1-+---+------+---------+-----+-----+
When using the gpio tool, we are specifically interested in the “wPi” columns.
The eight LED circuits established on each pi are hooked into a unique GPIO (wiring pi numbers 0-7).
When the pin is active (3.3V applied, the 'true' or 1 state), the LED will be lit up (turned ON).
When the pin is inactive (0V applied, the 'false' or 0 state), the LED will be OFF.
If you look in the table for wiringPi pins 0-7, you'll see under the “Mode” column that all the needed pins are set to IN or “input” mode (expecting to read data in).
To utilize the LEDs, we need to instead OUTPUT from the pins.
A mode change is needed, which can be accomplished with the gpio command, mode parameter. It requires the wiringPi pin number (0-7), and the desire mode to set it to (in, out).
To set wiringPi GPIO pin 0 for output mode, for instance, we'll want to do this:
pi@pi1b_0#:~ $ gpio mode 0 out
You may want to repeat (or loop) this for the remaining pins.
To modify the state of the pin (it can be in a '0' or '1' state), we once again use the gpio command, with the write parameter. It requires the wiringPi pin number (0-7) and the state we wish it to become (0 is OFF, or 1 being ON).
To write a 1 to wiringPi GPIO pin 0, we'll want to do this:
pi@pi1b_0#:~ $ gpio write 0 1
Similarly, to turn it back off again, we'll want to write a zero there:
pi@pi1b_0#:~ $ gpio write 0 0
You will want to perform similar actions on the other LED-wired pins to create the desired situations as required by this project.
It is your task to write 4 scripts, specifications laid out as follows:
A useful bit of logic, appropriately setting the pin modes to OUTPUT and turning the pins to an OFF state is likely something your other scripts will want to call upon before they perform their intended tasks.
Therefore, you will start by writing a script you can run that establishes a sane operating environment for your LED manipulations.
This script should make use of a loop to perform its task (setting OUTPUT mode and WRITING a 0 state to the pin).
It is not by accident the LEDs were build next to each other, wired up in sequential fashion as they are. The intention was to create an 8-bit quantity that you could manipulate.
So, it is your task for this script to write a visual “binary counter”, that, lacking any arguments, starts at 0 (00000000), and with a short delay between each state change (say, no less than 0.5 seconds), increments one at a time until it reaches 255 (11111111), where 0 indicates an LED in OFF position, and 1 indicates an LED in ON position.
You will want to create your visual output in standard observed form for binary numbers (ie the left side denotes the MOST SIGNIFICANT BIT, and the right-most side denotes the LEAST SIGNIFICANT BIT).
For example, if displaying the number 13 with this script, our binary value being output should be:
0 0 0 0 1 1 0 1
Where 2^7=0, 2^6=0, 2^5=0, 2^4=0, 2^3=1, 2^2=1, 2^1=0, and 2^0=1.
Also, the script should accept the following optional arguments:
Unless you merge in the decrementing script logic into this script, you should do error checking to ensure that the starting point is LOWER than the ending point, otherwise display an error message and exit, leaving the LEDs in an OFF state.
If you DO choose to incorporate decrement logic into this same script, a starting point being HIGHER than the ending point indicates the script should decrement instead of increment.
If ONLY a step and starting value is given, proceed from that point to the final bound (being an incrementer if step is positive, or decrementer if step is negative).
Like the script above, only its default behavior is to decrement instead of increment.
NOTE that you CAN combine script2 and script3 into ONE script, with the appropriate supporting logic to handle both modes.
The purpose of this script is to create a fancy flashing pattern, lighting up and turning off the LEDs to create wavy or “back and forth” style visual effects.
Evaluation will be based on correctness of values as well as on commenting/formatting/indentation/spacing of scripts.
To be sure, I'll be checking to make sure you solution follows the spirit of what this project is about (that you implement functional, flowing logic utilizing the tools and concepts we've learned, in an application that helps demonstrate your comprehension). Don't try to weasel your way out of this or cut corners. This is an opportunity to further solidify your proficiency with everything.
The spirit of the project embodies many aspects we've been focusing on throughout the semester:
Basically: I want your solution to be the result of an honest, genuine brainstorming process where you have figured out a path to solving the problem, you have dabbled and experimented and figured things out, and you can command the concepts and tools with a fluency enabling you to pull off such a feat. Your solution should demonstrate the real learning that took place and experience gained.
Cutting corners, avoiding work, skimping on functionality, cheating through getting others to do work for you or finding pre-packaged “answers” on the internet violates the spirit of the project, for they betray your ability to pull off the task on your own.
I would also like it if you provided an inventory of what functionality is lacking or out of spec when you submit the project. The better you can describe your deviations from stated requirements, the more forgiving I may be during evaluation (versus trying to hide the shortcomings and hoping I do not discover them).
The more fluent you are in describing your shortcomings on accomplishing the project (ie “I didn't know how to do this” is far from fluent), the better I will be able to gauge your understanding on a particular aspect.
This can be in the form of comments in your script, or even a separate file submitted at time of submission (if a file, be sure to make mention of it in your script so I can be sure to look for it).
By successfully performing this project, you should have a fully functioning set of scripts by the names script1 through script4 (possibly lacking script3 if you've merged functionality with script2), which are all you need to submit for project completion (no steps file, as your “steps” file ARE the scripts you wrote).
To submit this project to me using the submit tool, run the following command at your lab46 prompt:
$ submit unix spf1 script1 script2 script3 script4 Submitting unix project "spf1": -> script1(OK) -> script2(OK) -> script3(OK) -> script4(OK) SUCCESSFULLY SUBMITTED
You should get some sort of confirmation indicating successful submission if all went according to plan. If not, check for typos and or locational mismatches.
I'll be looking for the following:
52:spf1:final tally of results (52/52) *:spf1:scripts submitted in accordance with specifications [4/4] *:spf1:initialization script logic present and functions [4/4] *:spf1:initialization logic uses loop to automate task [4/4] *:spf1:incrementation script logic present and functions [4/4] *:spf1:counter script logic is centrally based on loop [4/4] *:spf1:counter script logic does adequate error checking [4/4] *:spf1:decrementation script logic present and functions [4/4] *:spf1:flashy script logic present and functions [4/4] *:spf1:scripts appropriately call the initialization logic [4/4] *:spf1:scripts are organized and easy to read [4/4] *:spf1:scripts effectively utilize selection structures [4/4] *:spf1:scripts effectively utilize looping structures [4/4] *:spf1:scripts are proper bash scripts with shabang and exit [4/4]
Additionally: