mirror of
https://github.com/alexandrebobkov/ESP-Nodes.git
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161 lines
6.8 KiB
ReStructuredText
161 lines
6.8 KiB
ReStructuredText
HOW DOES IT WORK?
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=================
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The BitByteRider RC car is powered by ESP32-C3 Breadboard & Power adapter developmemt board.
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The Schematic and KiCAd PCB board are available on GitHub_: https://github.com/alexandrebobkov/ESP32-C3_Breadboard-Adapter
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.. _GitHub: https://github.com/alexandrebobkov/ESP32-C3_Breadboard-Adapter
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Reserved Pins & GPIOs
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---------------------
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The following table summarizes GPIOs and pins reserved for operations purposes.
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The GPIO numbers correspond to those on the ESP32-C3 WROOM microcontroller. The Pin number corresponds to the pin on the Breadboard and Power adapter development board.
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x- and y- axis
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~~~~~~~~~~~~~~
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The **GPIO0** and **GPIO1** assigned to measuring the voltage of x- and y- axis of the Joystick. Lastly, there is a group of GPIO pairs responsible for PWM for DC motors.
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Direction and Speed
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~~~~~~~~~~~~~~~~~~~
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The pairs of DC motors on the left side are wired to the dedicated PWM channels. This means that *ESP32-C3 Breadboard DevBoard* can control rotation speed and direction of DC motors in pairs only (i.e. left and right side).
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Consequently, only four PWM channels are sufficient for controlling the direction of the RC car.
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Based on this constraint, the RC car can only move front, back, and turn/rotate left and right. Any other movements are not possible (i.e. diagonal or sideways).
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.. note::
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What is PWM?
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PWM (Pulse Width Modulation) is a technique used to simulate analog voltage levels using digital signals. It works by rapidly switching a
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digital pin between HIGH (on) and LOW (off) states at a fixed frequency. The duty cycle—the percentage of time the signal is HIGH in one
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cycle—determines the effective voltage delivered to a device.
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A pair of PWM channels are required for defining rotation speed and direction of the DC motors on each side.
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In particular, **GPIO6** and **GPIO5** provide PWM to the left- and right- side DC motors to rotate in a **clockwise** direction.
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Similarly, **GPIO4** and **GPIO7** provide PWM to the left- and right- side DC motors to rotate in a **counter-clockwise** direction.
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Changing PWM on each channel determines the speed and direction of the RC car.
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The following images illustrate various PWM duty cycles registered by oscilloscope (duty cycles 0%, 48% and 91%, resp.).
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.. figure:: _static/ESP-IDF_Robot_PWM_Duty-0.bmp
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DC Motor PWM duty cycle 0%
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.. figure:: _static/ESP-IDF_Robot_PWM_Duty-50.bmp
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DC Motor PWM duty cycle 47.6%
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.. figure:: _static/ESP-IDF_Robot_PWM_Duty-95.bmp
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DC Motor PWM duty cycle 90.8%
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.. raw:: html
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<br/><br/><br/><br/>
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+------+-----+---------------------------------------------------------+----------------+
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| GPIO | Pin | Function | Notes |
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+======+=====+=========================================================+================+
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| 0 | 16 | Joystick x-axis | ADC1_CH0 |
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+------+-----+---------------------------------------------------------+----------------+
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| 1 | 15 | Joystick y-axis | ADC1_CH1 |
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+------+-----+---------------------------------------------------------+----------------+
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| 8 | 5 | Joystick push button | |
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+------+-----+---------------------------------------------------------+----------------+
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| 6 | 4 | PWM for clockwise rotation of left-side motors | LEDC_CHANNEL_1 |
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+------+-----+---------------------------------------------------------+----------------+
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| 5 | 3 | PWM for clockwise rotation of right-side motors | LEDC_CHANNEL_0 |
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+------+-----+---------------------------------------------------------+----------------+
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| 4 | 2 | PWM for counter-clockwise rotation of right-side motors | LEDC_CHANNEL_2 |
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+------+-----+---------------------------------------------------------+----------------+
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| 7 | 6 | PWM for counter-clockwise rotation of left-side motors | LEDC_CHANNEL_3 |
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+------+-----+---------------------------------------------------------+----------------+
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Fusion of Software with Hardware
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--------------------------------
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The *struct* for storing motors PWM values.
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.. code-block:: c
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struct motors_rpm {
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int motor1_rpm_pwm;
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int motor2_rpm_pwm;
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int motor3_rpm_pwm;
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int motor4_rpm_pwm;
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};
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The function for updating motors' PWM values.
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.. code-block:: c
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// Function to send data to the receiver
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void sendData (void) {
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sensors_data_t buffer; // Declare data struct
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buffer.crc = 0;
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buffer.x_axis = 0;
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buffer.y_axis = 0;
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buffer.nav_bttn = 0;
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buffer.motor1_rpm_pwm = 0;
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buffer.motor2_rpm_pwm = 0;
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buffer.motor3_rpm_pwm = 0;
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buffer.motor4_rpm_pwm = 0;
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// Display brief summary of data being sent.
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ESP_LOGI(TAG, "Joystick (x,y) position ( 0x%04X, 0x%04X )", (uint8_t)buffer.x_axis, (uint8_t)buffer.y_axis);
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ESP_LOGI(TAG, "pwm 1, pwm 2 [ 0x%04X, 0x%04X ]", (uint8_t)buffer.pwm, (uint8_t)buffer.pwm);
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ESP_LOGI(TAG, "pwm 3, pwm 4 [ 0x%04X, 0x%04X ]", (uint8_t)buffer.pwm, (uint8_t)buffer.pwm);
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// Call ESP-NOW function to send data (MAC address of receiver, pointer to the memory holding data & data length)
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uint8_t result = esp_now_send(receiver_mac, &buffer, sizeof(buffer));
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// If status is NOT OK, display error message and error code (in hexadecimal).
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if (result != 0) {
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ESP_LOGE("ESP-NOW", "Error sending data! Error code: 0x%04X", result);
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deletePeer();
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}
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else
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ESP_LOGW("ESP-NOW", "Data was sent.");
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}
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The onDataReceived() and onDataSent() are two call-bacl functions that get evoked on each corresponding event.
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.. code-block:: c
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// Call-back for the event when data is being received
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void onDataReceived (uint8_t *mac_addr, uint8_t *data, uint8_t data_len) {
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buf = (sensors_data_t*)data; // Allocate memory for buffer to store data being received
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ESP_LOGW(TAG, "Data was received");
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ESP_LOGI(TAG, "x-axis: 0x%04x", buf->x_axis);
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ESP_LOGI(TAG, "x-axis: 0x%04x", buf->y_axis);
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ESP_LOGI(TAG, "PWM 1: 0x%04x", buf->motor1_rpm_pwm);
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}
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// Call-back for the event when data is being sent
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void onDataSent (uint8_t *mac_addr, esp_now_send_status_t status) {
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ESP_LOGW(TAG, "Packet send status: 0x%04X", status);
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}
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The rc_send_data_task() function runs every 0.1 second to transmit the data to the receiver.
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.. code-block:: c
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// Continous, periodic task that sends data.
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static void rc_send_data_task (void *arg) {
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while (true) {
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if (esp_now_is_peer_exist(receiver_mac))
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sendData();
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vTaskDelay (100 / portTICK_PERIOD_MS);
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}
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}
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Schematic
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---------
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.. image:: _static/ESP-IDF_Robot_schematic.png |