6. Embedded programing

Assignments in this week

Group Assignment:
- [x] browse through the data sheet for your microcontroller
- [x] compare the performance and development workflows for other architectures

Individual assignment:
- [x] write a program for a microcontroller development board that you made
- [x] to interact (with local input &/or output devices)
- [x] and communicate (with remote wired or wireless devices)
- [x] extra credit: use different languages &/or development
- [x] extra credit: connect external components to the board

Group Assignment

• Group Assignment Link

Datasheet of different microcontrollers

Comparison with diffrent microcontrollers.

RP2040 vs STM32 vs SAMD21 vs ESP32-S3

	Raspberry Pi RP2040	STM32F103C8T6	ATSAMD21G18	ESP32-S3
Product Image
Dev Board	Raspberry Pi Pico	Blue Pill	MKRZero, Seeed XIAO	ESP-S3, Seeed XIAO
Cores	Dual-Core	Single Core	Single Core	Dual-Core
Core Architechture	32-bit ARM Coretex-M0+	32-bit ARM Coretex-M3	32-bit ARM Coretex-M0+	Xtensa® 32-bit LX7
	Flexible Clock up to 133MHZ	72MHz	48MHz	Up to 240 MHz
RAM Size	264 KByte SRAM	20 KByte	32 KByte	512 KByte SRAM
Flash Size	Up to 16 MByte external Flash	64 KByte	256 KByte	Up to 1 GByte external Flash
DIrect Memory Access	12 x DMA	7 x DMA	12 x DMA	3 x DMA
Wireless	None	None	None	IEEE 802.11b/g/n
Programming Lanuage	MicroPython, CircuitPython, C/C++, Arduino	C alike, Arduino IDE	C alike, Arduino IDE	Espressif IDF, Arduino IDE, CircuitPython
MCU Power Voltage	3.3VDC	3.3VDC	3.3VDC	3.3VDC
USB Interface	USB 1.1 Device and Host	USB 2.0 Full Speed	USB OTG	USB OTG
Program Laoding	USB Mass Storage, UF2	External device, Serial	USB, UF2	USB, UF2
GPIO	30 x Digital Input/Output	37 x GPIO	38 x GPIO	45 x GPIO
High-Speed PIO	2 blocks, 8 x State Machine, 8 × 10	No	No	No
ADC	4 x 12-bit	10 x 12-bit	12 x 12-bit	2 × 12-bit SAR ADCs, up to 20 channels
DAC	No	No	1 x 10-bit	2 x 8-bit
UART	2	3	6 x Sercom (UART, I2C, SPI)	3
I2C	2	2	6 x Sercom (UART, I2C, SPI)	2
SPI	2	3	6 x Sercom (UART, I2C, SPI)	4
PWM	16	15	20	2 × MCPWM
On Chip Sensor	Temperature	No	No	Temperature
IC Package	QEN-56	LQFP-48	48-pin TQFP, QFN, WLCSP	VFQFN-56
Retail Price	USD 1.00	USD 3.50	USD 3.15	USD 1.20

Reference

• Datasheet of Raspberry Pi RP2040
• Datasheet of Microchip ATSAM21G18A
• Datasheet of ESP32S3

In this week’s course, I learned various knowledge about embedded programming. As a former embedded engineer, we will all retain the habit of studying datasheets. Based on the classification of microcontrollers that are currently on the market, I selected several important specifications to study and read, such as RP2040,STM32,ATSAMD12,ESP32-S3.
In terms of length, RP2040 is currently the most detailed datasheet.According to the latest information, 640 pages of information detail the origin, parameters and usage specifications of the chip. As a former embedded engineer, we often pay more attention to the performance processing parameters of the chip and some interface design references, so that developers and engineers can design chip reference development boards according to their own needs.

Programing on XIAO ESPS3

1. Install Arduino IDE and board manager

Installing the Arduino Ide is a relatively painless task. But when I installed the board manager according to Seeed XIAO’s WIKI, an error occurred. The main reason for the error was due to the timeout of loading the github library resources. After continuous inquiries, I found the reason. Due to VPN problems, I was unable to obtain the library files in real time, which resulted in the loading failure.

2. Sample code for LED Blink

After successfully installing the library files, you can finally select the board model in the Arduino IDE. I used the Blink program in the sample program. By compiling and uploading the program, I can finally see that the right LED of XIAO ESP32 flashes.

3. Microphone Testing for XIAO ESP32 Sense

According to XIAO’s product introduction, the board integrates peripherals such as a microphone, so I will follow the tutorial to test the microphone peripherals and train through edge pulse.
- A. Initialize the Micro SD card: Since XIAO ESP32 requires a memory card in FAT32 format, I first found a memory card to initialize it to facilitate subsequent storage of sound files collected by the microphone.
- B. Test the microphone function and monitor the sound through the serial port: After compiling and uploading the program, we can set the corresponding baud rate through the serial port for signal observation. After shouting to XIAO loudly, we can clearly see the signal displayed on the serial port. The value increases and changes occur.

Sample Code for XIAO ESP32S3 Microphone Testing

  #include <I2S.h>
        void setup() {
          // Open serial communications and wait for port to open:
          // A baud rate of 115200 is used instead of 9600 for a faster data rate
          // on non-native USB ports
          Serial.begin(115200);
          while (!Serial) {
            ; // wait for serial port to connect. Needed for native USB port only
          }     
          // start I2S at 16 kHz with 16-bits per sample
          I2S.setAllPins(-1, 42, 41, -1, -1);
          if (!I2S.begin(PDM_MONO_MODE, 16000, 16)) {
            Serial.println("Failed to initialize I2S!");
            while (1); // do nothing
          }
        }
        void loop() {
          // read a sample
          int sample = I2S.read();     
          if (sample && sample != -1 && sample != 1) {
            Serial.println(sample);
          }
        } 

4. XIAO ESP32S3 Sense Keywords Spotting via TinyML EdgeImpules

• A.Capturing the offline audio data:
  As we all know, if you need to train an AI model, the first step you need to do is to obtain the original data set to facilitate subsequent model training. According to the tutorial, we collected 2 sets of data respectively with the keywords “hello” and “crail” through XIAO ESP32S3. Each set of data is about 10 seconds in length, and finally saved in the microSD card. Since I am currently just testing, there are not many data samples collected. If you want to conduct more accurate AI model training, more data sets will be more helpful for model generation.
  
• B.Uploading collected sound data to Edgeimpluse then make pre-processing and model defining:
  

Programing on XIAO RP2040

1.Install the XIAO RP2040 libaray

• Add the reference link to Arduino IDE preference setting.

https://github.com/earlephilhower/arduino-pico/releases/download/global/package_rp2040_index.json

- Select the Board and Com Port as XIAO RP2040.

2.Use the button to light up the LED

In this program, I first referred to the schematic diagram to find the corresponding GPIO interfaces of the onboard RBG LED and buttons. I was familiar with Arduino programming and Neopixel library file control LED before, so I wanted to control the RGB_LED to turn on and off by pressing the button, and at the same time, long press the button to make the color of the RGB LED change. When the button is released, the light The color will stay in the state just shown.
Use the button to light up the RGB_LED

In this part, it is mainly used to call some library files and set the pins of the hardware connection, and at the same time define some parameters related to the library files. I set three pins here, define the number of RGB LEDs and detect double-press. button time.

#include <Adafruit_NeoPixel.h>
int Power = 11; // RGB_LED Power GPIO
int PIN = 12; // RGB_LED Signal GPIO
int ButtonPin = 27;  // Button GPIO
#define NUMPIXELS 1 // Numbers of RGB_LED
#define DOUBLE_PRESS_TIME 500 // Maximum time for double press detection in milliseconds
Adafruit_NeoPixel pixels(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);

In this part, it is mainly the initialization part of the program. First, initialize the library file of the LED light. In addition, set the brightness of the LED light. Since the brightness of the lamp bead was too bright during the previous test, I set it in the initialization. In addition, some pin function settings are performed.

void setup() {
  pixels.begin();
  pixels.setBrightness(50);  // Set the LED brightness
  pinMode(Power, OUTPUT);
  digitalWrite(Power, HIGH);
  pinMode(ButtonPin, INPUT_PULLUP);  
  // Set the button pin as an input and enable the internal pull-up resistor
}

In this part, we mainly define some variable parameters, especially the initial value for the detection volume of key detection.

bool lastButtonState = HIGH;  // lastbutton State
int rainbowIndex = 0;  // Index for tracking rainbow colors
bool rgbOn = true;  // RGB LED initial state
unsigned long lastPressTime = 0;  // Time of the last button press
int pressCount = 0;  // Button press count

In this part, enter the main function part of the program. First, initialize and read the button status, then light up the LED and complete the operation actions I set before.

void loop() {
  bool currentButtonState = digitalRead(ButtonPin);
  unsigned long currentTime = millis();
  // Displays rainbow colors if button is not pressed and RGB LED is on
  if (rgbOn && currentButtonState == HIGH) {
    rainbowIndex++;
    if (rainbowIndex > 255) {
      rainbowIndex = 0;
    }
    pixels.setPixelColor(0, Wheel(rainbowIndex));  // Set rainbow colors
    pixels.show();
    delay(20);  // Adjust the speed to change how quickly the color changes
  }
  // Detect button state changes from unpressed to pressed
  if (lastButtonState == HIGH && currentButtonState == LOW) {
    pressCount++;
    if (pressCount == 1) {
      lastPressTime = currentTime;
    } else if (pressCount == 2 && (currentTime - lastPressTime <= DOUBLE_PRESS_TIME)) {
      rgbOn = !rgbOn;  // Toggle RGB LED state
      if (!rgbOn) {
        pixels.clear();
        pixels.show();
      }
      pressCount = 0;  // Reset press count
    } else if (pressCount > 2 || (currentTime - lastPressTime > DOUBLE_PRESS_TIME)) {
      pressCount = 1;  // Reset press count and start over
      lastPressTime = currentTime;
    }
  }
  lastButtonState = currentButtonState;  // Update button state
}
// Use wheel functions to generate rainbow colors
uint32_t Wheel(byte WheelPos) {
  WheelPos = 255 - WheelPos;
  if (WheelPos < 85) {
    return pixels.Color(255 - WheelPos * 3, 0, WheelPos * 3);
  }
  if (WheelPos < 170) {
    WheelPos -= 85;
    return pixels.Color(0, WheelPos * 3, 255 - WheelPos * 3);
  }
  WheelPos -= 170;
  return pixels.Color(WheelPos * 3, 255 - WheelPos * 3, 0);
}

Press the button light up the RGB LED；
Long-time press button to make RGB LED change color;
Release button the freeze the current RGB LED color;
Doube-press button to light off the RGB LED;