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--- en:iot-open:practical:hardware:sut:esp32:emb9a_1 [2024/02/29 16:31] – [Suggested Readings and Knowledge Resources] pczekalski
+++ en:iot-open:practical:hardware:sut:esp32:emb9a_1 [2024/03/22 10:00] (current) – [Project information] pczekalski
@@ Line 1: / Line 1: @@
-====== EMB9A: Reading colour sensor =====
+====== EMB9A: Use of RGB LEDs =====
-A colour sensor (TCS 34725) can detect the brightness and colour of the light emitted. It works with the I2C; in our laboratory, each sensor has a fixed 0x29 address in the I2C bus. The sensor is in the black enclosure, ensuring no ambient light impacts readings. The only light source is an RGB LED, controlled as described in the scenario [[en:iot-open:practical:hardware:sut:esp32:emb9b_1|EMB9B]]. This is another LED connected parallel to the one you can observe in the camera.
+This scenario presents how to handle the brightness control of the tri-coloured LEDs. One is observable via camera, as presented in the figure (component 9A), while another is hidden inside the black enclosure and lights a colour sensor (component 9B). Both LEDs are electrically bound and cannot be controlled independently. Those LEDs have 3 colour channels, controlled independently: R (Red), G (Green) and B (Blue). Mixing of those colours creates other ones, such as pink and violet. Each R G B channel can be controlled with a separate GPIO to switch it on or off or control brightness using a PWM signal, as presented in this tutorial.
 ===== Prerequisites =====
-To implement this scenario, it is necessary to get familiar with the following scenarios first:
+A good understanding of the PWM signal and duty cycle is necessary. We also use built-in timers to control the PWM hardware channels of the ESP32 chip. In this case, we do not use an external library; instead, we use built-in tools in the Arduino framework for ESP32 so that no additional libraries will be included in the project.
-  * [[en:iot-open:practical:hardware:sut:esp32:emb5_1|EMB5: use of the LCD display to present current reading of the light sensor]],
-  * [[en:iot-open:practical:hardware:sut:esp32:emb9b_1|EMB9: how to control RGB LED with PWM, to light the sensor]].
-To simplify TCS sensor use, we will use a dedicated library:
-<code bash>
-lib_deps = adafruit/Adafruit TCS34725@^1.4.2
-</code>
-<note important>Also, remember to add the LCD handling library, as present in the EMB9 scenario, unless you decide to use another output device.</note>
 ===== Suggested Readings and Knowledge Resources =====
   * [[en:iot-open:introductiontoembeddedprogramming2:cppfundamentals]]
   * [[en:iot-open:hardware2:esp32|]]
+  * [[en:iot-open:hardware2:actuators_light|]]
   * [[en:iot-open:practical:hardware:sut:esp32|]]
   * [[en:iot-open:embeddedcommunicationprotocols2:pwm|]]
-  * [[en:iot-open:hardware2:sensors_optical|]]
 ===== Hands-on Lab Scenario =====
 ==== Task to be implemented ====
-//Describe a task to be implemented by the scenario user.//
+Implement a program that will light LEDs consecutively with R, G, and B. Use 50% of the maximum brightness. Use a PWM signal to control each GPIO for R, G and B, each colour separately to let you easily observe it.
 ==== Start ====
-//Write starting conditions, i.e. what to do in the beginning, what to pay attention to before beginning, how the mechanical part should look, etc.// Include needed compiler configuration, etc.
+Assuming you will use 8-bit PWM resolution, the minimum value is 0, and the max (full brightness) is 255. Note that full brightness may be too bright for the observation camera, so consider using a range between 0 and 60 (eventually up to 100).
 ==== Steps ====
-// Write some extra information if, i.e. some steps are optional; otherwise, cancel this paragraph (but do not remove the header).//
+To use PWM in ESP32, it is best to use built-in ''ledc*'' functions [[https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-reference/peripherals/ledc.html|LEDC documentation on the ESP32 manufacturer's page]].
+The ''leds'' use timers and have channels attached to the timer. We will use 1 channel per colour (R, G and B, so 3 in total). A PWM frequency is controlled with the timer to be shared for all 3 R, G and B channels. Channels control the PWM duty cycle.
 === Step 1 ===
-//Describe activities done in Step 1.//
+Define some parameters, including channel numbers, PWM resolution (here 8-bit) and PWM frequency (5000Hz):
+<code c>
+#define RGBLED_B_PIN 26
+#define RGBLED_G_PIN 21
+#define RGBLED_R_PIN 33
-...
+#define PWM1_Ch    5
+#define PWM2_Ch    6
+#define PWM3_Ch    7
-=== Step n ===
+#define PWM_Res   8
-//Describe activities done in Step n.//
+#define PWM_Freq  5000
+</code>
+GPIO pins controlling  LEDS are 33 (Red), 21 (Green) and 26 (Blue), respectively.
+=== Step 2 ===
+Initialise 3 channels for PWM and make them dark:
+<code c>
+    ledcSetup(PWM1_Ch, PWM_Freq, PWM_Res);
+    ledcSetup(PWM2_Ch, PWM_Freq, PWM_Res);
+    ledcSetup(PWM3_Ch, PWM_Freq, PWM_Res);
+    ledcAttachPin(RGBLED_R_PIN, PWM1_Ch);
+    ledcAttachPin(RGBLED_G_PIN, PWM2_Ch);
+    ledcAttachPin(RGBLED_B_PIN, PWM3_Ch);
+    delay(100);
+    ledcWrite(PWM1_Ch,0);
+    ledcWrite(PWM2_Ch,0);
+    ledcWrite(PWM3_Ch,0);
+</code>
+To control the LED (via PWM), use ''ledcWrite(PWM_Channel, duty_cycle_value);''.
+=== Step 3 ===
+Write a loop for each colour (R, G, then B) to light the colour from dark to max value (60 or 100, give it a test).
+<note important> Full duty cycle (255) will be too bright for the remote access video camera to handle it. Use some reasonable range such as 0..60 or 0..100 is strongly advised.</note>
+Mind to compose code to increase and decrease each colour. A hint is below (PWM Channel 3 so that controls Blue):
+<code c>
+  // Increase brightness
+  for (int dutyCycle = 0; dutyCycle <= 100; dutyCycle++) {
+    // Gradually increase duty cycle for Red LED
+    ledcWrite(PWM3_Ch, dutyCycle);
+    delay(20); // Delay for smooth transition
+  }
+  delay(100);
+  // Decrease brightness
+  for (int dutyCycle = 100; dutyCycle >= 0; dutyCycle--) {
+    // Gradually decrease duty cycle for Red LED
+    ledcWrite(PWM3_Ch, dutyCycle);
+    delay(20); // Delay for smooth transition
+  }
+</code>
+<note>There is a number of handy functions in the ''ledc'' library, including (among others):
+  * ''analogWrite(pin,value);'' to keep compatibility with genuine Arduino,
+  * ''ledcFade(pin, start_dutycycle, end_dutycycle, fade_time_ms);'' that you can use instead of the loop above,
+  * ''ledcDetach(pin);'' to detach a pin from the channel (and thus release the PWM channel),
+  * ''ledcWriteNote(pin, note, octave);'' where ''note'' is one of the values: NOTE_C, NOTE_Cs, ... (and so on, music notes, up to NOTE_B) - it is useful when PWM controls a speaker, to generate a perfect musical note, but we do not use speakers here, sorry.
+</note>
 ==== Result validation ====
-//Provide some result validation methods for self-assessment.//
+You should be able to observe the pulsing colours of the RGB LED, increasing and decreasing brightness linearly.
 ===== FAQ =====
-This section is to be extended as new questions appear. \\
-When using the printed version of this manual, please refer to the latest online version of this document to obtain the valid and up-to-date list of the FAQ.
-//Provide some FAQs in the following form:\\
-**Question?**: Answer.
-//
+**What if I bind a PWM channel to more than one GPIO?**: As you control the duty cycle writing to the channel rather than the GPIO, you will control those GPIOs simultaneously (in parallel) with the same signal. That can be handy to control parallelly separate devices that should behave the same way, i.e. servos.
+\\
+**What is the maximum number of channels?**: the MCU we use here is ESP32-S3, so it has 8 PWM channels. You can use timers and software implementation of the PWM signal if you need more, but that is a bit tricky and may not be as precise as hardware PWM implementation.
+\\
+**What is the maximum bit resolution for PWM?**: it is between 1 and 14 bits in this particular MCU.
+\\
+**What PWM frequency should I use?**: there is no straightforward answer to this question: assuming you observe LED remotely with a camera, even 50Hz would be enough. But it would give a severe flickering experience to the live user, on the other hand. In the example above, we propose 5kHz, which this MCU can easily handle.
+<WRAP noprint>
 ===== Project information =====
 {{:en:iot-open:logo_iot_200_px.png?200|}}\\
@@ Line 62: / Line 112: @@
 {{:en:iot-open:ccbync.png?100|}}
 </figure>
+</WRAP>

en/iot-open/practical/hardware/sut/esp32/emb9a_1.1709224265.txt.gz · Last modified: 2024/02/29 16:31 by pczekalski