I have (technically had because it smoked) a PCB board with an ESP32 Dev Board plugged in. I had 4 external ADCs. ADC 1 and 2 were on hspi and ADC 3 and 4 were on vspi (doesn't matter if hspi/vspi are switched). When I run the code with the ESP32 powered via my USB everything works fine. When I remove the power and rely solely on L7805CV to supply 5V to the ESP's 5V pin ADC 3 and 4 stop working. I cut my USB cable off and touched the 5V on the USB directly to the 5V on the ESP32 and ADC pin 3 and 4 came alive. This makes me think the issue is with the supply voltage level.
As far as the hardware/wiring is concerned I had everything connected to the same ground. The L7805CV was nowhere near its current rating (was only slightly warm) but I did notice that the voltage on the L7805CV was only 4.97V while the voltage from the USB was 5.01V. Could this be causing the issue? I need to redesign my board and I'm trying to understand why I was seeing this issue.
Here is the code I used to read the 4 channels. I tried really long delays before and after setting the pins high and low and didn't make a difference. The highlights (I think) are the pins I used (SPI1_SCK = 14; SPI1_MISO = 12; ADC_CS_1 = 15; ADC_CS_2 = 21; SPI2_SCK = 18; SPI2_MISO = 19; ADC_CS_3 = 25; ADC_CS_4 = 26;)
#include <Arduino.h>
#include <SPI.h>
#include <HardwareSerial.h>
const int SPI1_SCK = 14;
const int SPI1_MISO = 12;
const int ADC_CS_1 = 15;
const int ADC_CS_2 = 21;
const int SPI2_SCK = 18;
const int SPI2_MISO = 19;
const int ADC_CS_3 = 25;
const int ADC_CS_4 = 26;
unsigned char upper_byte;
unsigned char middle_byte;
unsigned char lower_byte;
unsigned int data;
//uninitalised pointers to SPI objects
SPIClass vspi(VSPI);
SPIClass hspi(HSPI);
// function declarations
int readData(SPIClass*, unsigned int);
// RS485 properties
HardwareSerial SerialPort(2); //UART2 on ESP32 module
const int RXpin = 16; //pin 16 recommended for RXD
const int TXpin = 17; //pin 17 recommended for TXD
const int slave_address = 102; //address must be hard coded (will not auto generate)
int regs[256]; //register array available to master
bool debug_read_esp = false;
bool debug_read_all = false; // only will read data coming to ESP32, good to determine if communication exists
bool debug_write = false;
const unsigned int numSamples = 40; // number of samples to take for each channel
void setup() {
Serial.begin(9600);
// Set up the first SPI interface
pinMode(ADC_CS_1, OUTPUT);
digitalWrite(ADC_CS_1, HIGH);
hspi.begin(SPI1_SCK, SPI1_MISO, -1, ADC_CS_1);
pinMode(ADC_CS_2, OUTPUT);
digitalWrite(ADC_CS_2, HIGH);
hspi.begin(SPI1_SCK, SPI1_MISO, -1, ADC_CS_2);
hspi.setClockDivider(SPI_CLOCK_DIV64); // ESP32 has SPI clock speed of 240MHz / 64 = 3.75MHz
hspi.setDataMode(SPI_MODE2); // CPOL = 1, CPHA = 0 (clock is high in idle state, data sampled on rising edge)
// Set up the second SPI interface
pinMode(ADC_CS_3, OUTPUT);
digitalWrite(ADC_CS_3, HIGH);
vspi.begin(SPI2_SCK, SPI2_MISO, -1, ADC_CS_3);
pinMode(ADC_CS_4, OUTPUT);
digitalWrite(ADC_CS_4, HIGH);
vspi.begin(SPI2_SCK, SPI2_MISO, -1, ADC_CS_4);
vspi.setClockDivider(SPI_CLOCK_DIV64); // ESP32 has SPI clock speed of 240MHz / 64 = 3.75MHz
vspi.setDataMode(SPI_MODE2); // CPOL = 1, CPHA = 0 (clock is high in idle state, data sampled on rising edge)
SerialPort.begin(9600, SERIAL_8N1, RXpin, TXpin); //UART: baud rate, serial config., rxd pin, txd pin
delay(2000);
SerialPort.flush();
Serial.flush();
}
void loop() {
unsigned int data_total_0 = 0;
unsigned int data_total_1 = 0;
unsigned int data_total_2 = 0;
unsigned int data_total_3 = 0;
//read the data into the registers
for (int i = 0; i < numSamples; i++){
data_total_0 += readData(&hspi, ADC_CS_1); // read data from channel 1
data_total_1 += readData(&hspi, ADC_CS_2); // read data from channel 2
data_total_2 += readData(&vspi, ADC_CS_3); // read data from channel 3
data_total_3 += readData(&vspi, ADC_CS_4); // read data from channel 4
}
regs[0] = data_total_0 / numSamples;
regs[1] = data_total_1 / numSamples;
regs[2] = data_total_2 / numSamples;
regs[3] = data_total_3 / numSamples;
// check for a modbus command over the serial port
if (SerialPort.available() > 7){
decode();
}
}
int readData(SPIClass* spi, unsigned int cs_pin) {
//Format is 0000UUUU MMMMMMMM LLLL0000
// returns 16 bit data
digitalWrite(cs_pin, LOW);
delay(1);
upper_byte = spi->transfer(0x00);
middle_byte = spi->transfer(0x00);
lower_byte = spi->transfer(0x00);
data = ((upper_byte << 12) | (middle_byte << 4) | (lower_byte >> 4));
digitalWrite(cs_pin, HIGH);
return data;
}
