high-voltage-pulse-generator
Master ESP32
SPI Communication with External Trigger and UART on ESP32
This project involves using an ESP32 to send data over SPI when two conditions are met:
- Data (frequency, pulse width, voltage amplitude, and channel) has been received over UART from user interface.
- An external trigger is detected on a specific pin. Simulating the optical detection of the droplet to be classified.
Both conditions must be fulfilled before the data is packed into a 32-bit integer and sent to the slave device over SPI. You can download the code here
1.- SPI protocol:
- Initialize SPI with mode 0, MSB first, and a clock speed of 1 MHz.
vspi.setDataMode(SPI_MODE0); # The clock line is low when idle. Data is captured on the rising edge of the clock and updated on the falling edge.
vspi.setBitOrder(MSBFIRST); # "MSB First", the most significant bit (the highest bit) of the byte is transmitted first, followed by the less significant bits.
pinMode(VSPI_SS, OUTPUT); # Configuring SS as output
vspi.begin(VSPI_SCLK, VSPI_MISO, VSPI_MOSI, VSPI_SS); # Initialization
- Data is sent in four bytes via SPI if dataToSend received from the user interface and External trigger pin is HIGH.
if (dataToSend != 0 && digitalRead(TRIGGER_PIN) == HIGH) {
vspi.beginTransaction(SPISettings(spiClk, MSBFIRST, SPI_MODE0));
digitalWrite(VSPI_SS, LOW);
vspi.transfer((dataToSend >> 24) & 0xFF); // Frequency
vspi.transfer((dataToSend >> 16) & 0xFF); // Pot_value
vspi.transfer((dataToSend >> 8) & 0xFF); // Pulse_width
vspi.transfer(dataToSend & 0xFF); // Channel
digitalWrite(VSPI_SS, HIGH);
vspi.endTransaction();
}
2.- UART protocol:
- Initialize serial communication considering the baud of the user interface for correct bilateral communication.
Serial.begin(9600); // Initializes serial communication at 9600 baud
delay(1000); // Waits to stabilize the ESP32
- Process Incoming UART Data: Read and parse incoming data as JSON, then pack the extracted values into a 32-bit integer.
if (Serial.available()) {
String input = Serial.readStringUntil('\n');
DynamicJsonDocument doc(1024);
deserializeJson(doc, input);
int frequency = doc["frequency"];
int pot_value = doc["pot_value"];
int pulse_width = doc["pulse_width"];
String channel_str = doc["channel"];
uint8_t channel = (channel_str == "ALL") ? 0 : channel_str.substring(2).toInt();
dataToSend = (frequency << 24) | (pot_value << 16) | (pulse_width << 8) | channel;
}
- Confirmation of sending and receiving data via serial port.
