Description

ECE40862: Software for Embedded Systems
Lab 2 – LED control using ADC, PWM, Timers and Interrupts

1. Overview
This assignment deals with 3 different peripherals, namely the PWM, ADC, and RTC on the ESP32 Feather Board. In addition to these peripherals, you will also be using timers and interrupts to implement LED control using a potentiometer and switch. The hardware and software implementation details for this assignment are described in the following sections.
2. Programming Exercise
2.1. Hardware Interfacing
Interface the following components to the board:
• An external push button switch as a GPIO (digital) input.
• An external potentiometer as an analog input.
• One external LED as a PWM (Pulse Width Modulation) output.
2.2. Software Implementation
Your program should implement the following functionalities.
>>> python ghosh37_lab2.py
Month? 9
Day? 22
Weekday? 2
Hour? 7
Minute? 30
Second? 00
Microsecond? 000000
• Initialize another hardware timer and read the analog input (potentiometer/pot values) every 100ms using the timer interrupt/callback and ADC. IMPORTANT: Connect the potentiometer only to a pin associated with ADC1 and not ADC2.
• Initialize and start a PWM signal on the external LED using a frequency of 10 Hz and a duty cycle of 256. The LED should start blinking at the defined frequency.
• In the beginning, rotating the pot should have no effect on the LED. The LED should continue blinking at predefined intensity and frequency.
• Detect a switch press using an interrupt/callback. Implement switch debouncing using another timer-based interrupt/callback. o Alternate switch presses should direct control towards either the frequency or the duty cycle of the LED. o The LED’s PWM signal frequency and duty cycle should be controlled by the pot readings.
o When you press the switch for the first time, the pot should control the LED’s PWM frequency. Now, if you rotate the pot, your LED should blink faster or slower, as the frequency of PWM changes. No change should occur in the LED’s intensity. o When you press the switch for the second time, the pot should control the LED’s PWM duty cycle. Now, if you rotate the pot, your LED’s intensity should be higher or lower, as the duty cycle of PWM changes. No change in the LED’s blinking frequency.
o The third switch press should revert the control back to the frequency, the fourth press should give control to the duty cycle and the process should continue forever.
3. Submission
Make sure you follow these submission instructions precisely. You need to turn in your code on Brightspace. Upload your source code as username_lab2.py where username is your CAREER account login ID. Do not ZIP the file. In addition, upload a README file named username_lab2_README.txt that contains a description of your hardware connections (which pins you used, exactly what they were connected to, etc.).
BONUS CREDIT: You will receive 20% bonus credit on the lab for creating a short video that shows you demonstrating your working solution (explain your hardware connections briefly before demonstrating the working solution). Please do not upload video files directly on Brightspace. Instead, upload the video to YouTube (or other such video hosting platform) and include the link to the video in your README file above.
4. Grading
REFERENCES
[1] Getting started with MicroPython on the ESP32 https://docs.micropython.org/en/latest/esp32/tutorial/intro.html
[2] ESP32 WROOM-32 Datasheet https://www.espressif.com/sites/default/files/documentation/esp32-wroom32_datasheet_en.pdf
[3] ESP32 Technical Reference Manual https://www.espressif.com/sites/default/files/documentation/esp32_technical_reference_ manual_en.pdf
[4] Adafruit HUZZAH32 – ESP32 Feather Online Manual https://learn.adafruit.com/adafruithuzzah32-esp32-feather
[5] Adafruit ESP32 Feather Schematics https://cdnlearn.adafruit.com/assets/assets/000/041/630/original/feather_schem.png?1494449413 [6] MicroPython GitHub https://github.com/micropython/micropython