SPI ADC Tutorial Initial Submission

content/tutorials/spi_adc_tutorial.md

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+---
+title: ESP32 SPI ADC Tutorial
+date: 2025-06-04
+authors:
+  - name: Luke Wittemann
+---
+
+
+# **ESP32 SPI ADC Tutorial**
+
+### 2025-05-19
+
+### By: Luke Wittemann
+___
+
+![image](./Team14Photos/SPI.png "SPI Communication")
+
+## Introduction
+
+In this tutorial, we will be learning to use an analog to digital 
+converter, or ADC, which communicates to our ESP32 using the SPI 
+serial interface. While many microcontrollers have built-in ADC's 
+for analogRead() functionality, they are often limited in temporal
+or voltaic resolution. By using an external ADC, you can select a 
+much more high performing component for more demanding appplications
+such as audio signal processing. 
+
+### Learning Objectives
+
+- How to wire up the ADC: what to connnect where
+- Code to interface with the ADC over SPI serial communication
+
+### Background Information
+
+ADC's are a part of many microcontroller based devices and are a main way for your microcontroller
+to interface with the world. Whether reading from a sensor, transducer, or simple voltage source, updated 
+and accurate readings are crucial to the success of an implementation. 
+
+## Getting Started
+
+This is a fairly simple tutorial with only a few required hardware and software components. You will need a computer with 
+Arduino IDE installed, a ESP32 based microcontroller, a MCP 3002 ADC, and a breadboard with some wire to connect everything
+together. *Other microcontrollers can be used, but the pins needed for SPI comminucation will likely be different.* This information 
+is commonly available due the prevalance of SPI as a method of serial communication. *Other ADC's can also be used, but the pinout
+and supply voltage requirements will likely vary.* Here, a main reason the MCP 3002 ADC is used is because it can be powered using
+ the ESP32's 3.3v pin and hence an external DC power supply is not required. 
+
+### Required Downloads and Installations
+
+- Arduino IDE
+
+### Required Components
+
+
+| Component Name   | Quanitity |
+| --------------   | --------- |
+|      ESP 32      |      1    |
+|Microchip MCP3002 |      1    |
+
+### Required Tools and Equipment
+
+Computer, breadboard, jumper wires
+
+## Part 01: Wiring and Physical Set-Up
+
+In this section, we are connect the ADC to our ESP32 such that we can program and test it. 
+
+- Plug the ADC chip, the **MCP3002**, into a breadboard.
+
+<img src="./Team14Photos/IMG_2562.JPG" alt="MCP on breadboard" width="600" height="800">
+
+- Following the pinout on the ADC's datasheet, connect VDD to the ESP32's 3.3v supply and VSS to ground. Connect
+    CLK(SCK), DOUT(MISO), DIN(MOSI), and CS(SS) to pins IO12, IO13, IO11, and IO10 respectively. These pins can also be altered 
+    to any digital pins if the default pins are in use by editing the pin selections at the top of the test script.
+
+<img src="./Team14Photos/IMG_2564.JPG" alt="ADC wired to ESP32" width="600" height="800">  
+
+![image](./Team14Photos/MCP3002.png "MCP3002 Pinout")
+
+- Connect your analog input to CH0. This chip can also be used as two inputs or as a single differential
+    input with CH0 or CH1 being the negative connection. *That being said, it is usually a good idea to buffer* 
+    *this input with a transistor or operational amplifier*. 
+
+
+## Part 02: Code and Programming
+
+In this section, we are going to program our ESP32 with the provided test code. 
+
+- Now that our circuit is built, we can begin programming by connecting the ESP32 to our computer using a USB-C cable
+
+<img src="./Team14Photos/IMG_2565.JPG" alt="USB connection" width="600" height="800">
+
+- To connect to the board, we need to make sure we have the board installed to our Arduino IDE. Go to the board manager
+    and install esp32 by Espressif Systems. 
+- Once the board package is installed, in Tools->Board, select ESP32S3 Dev Module
+- We should now see the ESP32 show up in the serial connections inside the Arduino IDE
+
+![image](./Team14Photos/ESP32arduinoIDE.png "ESP32 Connection in IDE")
+
+- Now, let's review the sample code before compiling it and uploading it to our microcontroller:
+```cpp
+    // include basic SPI library
+    #include <SPI.h>
+
+    // define SPI communication pins
+    #define PIN_CS   10
+    #define PIN_MISO 13
+    #define PIN_MOSI 11
+    #define PIN_SCK  12
+
+    // instantiate ADC object
+    SPIClass SPI_ADC(FSPI);  // Use FSPI bus for ESP32-S3
+
+    void setup() {
+    // initialize serial moniter
+    Serial.begin(115200);
+
+    // initialize SPI connection
+    SPI_ADC.begin(PIN_SCK, PIN_MISO, PIN_MOSI, PIN_CS);
+
+    // set chip select as output and start with pin high
+    pinMode(PIN_CS, OUTPUT);
+    digitalWrite(PIN_CS, HIGH);
+
+    }
+
+    void loop() {
+    // read from our ADC
+    uint16_t ADCreading = readADC();
+
+    // print the value
+    Serial.print("ADC reading: ");
+    Serial.print(ADCreading);
+    Serial.println("");
+
+    // short delay
+    delay(500);
+
+    }
+
+    // Function to read from our ADC over SPI
+    uint16_t readADC() {
+    // command to tell the ADC which mode to operate in
+    uint8_t command = 0b11010000;  // Start bit, single-ended CH0
+
+    // put chip select pin low which tells the ADC we are about to read from it
+    digitalWrite(PIN_CS, LOW);
+
+    // begin the SPI transaction
+    SPI_ADC.beginTransaction(SPISettings(1000000, MSBFIRST, SPI_MODE0));
+
+    // read our 10 bit value from the ADC in the form of two 8 bit(1 byte) transmissions
+    uint8_t highByte = SPI_ADC.transfer(command);
+    uint8_t lowByte = SPI_ADC.transfer(0x00);
+
+    // end the SPI transaction
+    SPI_ADC.endTransaction();
+
+    // put the chip select pin high which tells the ADC that we are done reading from it
+    digitalWrite(PIN_CS, HIGH);
+
+    // combine the two 8 bit transmissions into a single 16 bit result
+    uint16_t value = ((highByte & 0x03) << 8) | lowByte;  // 10-bit result
+
+    // return our 16 bit (only 10 bits are used) value
+    return value;
+    }
+```
+
+## Part 03: Example Using Adjustable DC Power Supply
+
+In this section, we are going test our setup by reading a adjustable DC voltage. If you don't have access to a DC power supply, 
+you can use a potentiometer, connecting the outer legs to ground and the 3.3v pin while connecting the middle leg with our ADC input. 
+
+- Connect your analog input to the CH0 pin of the MCP3002. In this case, I am simply connecting a DC power supply so that I can vary the voltage the ADC reads
+- As you adjust the voltage at the CH0 pin, either with a voltage divider and potentiometer, a adjustable DC power supply, or another analog voltage source like a sensor, you should see the serial moniter reading change. *Note: if your serial moniter reads 0, make sure Tools->USB CSD on Boot is enabled.* Since the ADC is 10 bits, you should see an value between 0 and 1023. In my case, 1023 represented 1.65v, which is half of the Vref or 3.3v. 
+
+<img src="./Team14Photos/IMG_2566.JPG" alt="ADC reading small voltage" width="600" height="800"> <img src="./Team14Photos/IMG_2567.JPG" alt="Serial moniter with small voltage" width="600" height="800">
+
+<img src="./Team14Photos/IMG_2568.JPG" alt="ADC reading larger voltage" width="600" height="800"> <img src="./Team14Photos/IMG_2569.JPG" alt="Serial moniter with larger voltage" width="600" height="800">
+
+## Conclusion
+
+Congratulations, you have started your embedded journey! With the ability to read accurate values from an analog voltage source, you can do all sorts of projects such 
+as light or sound detectors with the proper transducers. This ability will allow your microcontroller based projects to continually interact and react to the environment around them. 
+
+### Useful links
+-[ADC part page with datasheet](https://www.microchip.com/en-us/product/MCP3002)