4. Embedded programming

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Introduced to embedded programming

An embedded system is a computer system (a combination of a computer processor, computer memory, and input/output peripheral devices) that has a dedicated function within a larger mechanical or electronic system. Modern embedded systems are often based on microcontrollers.

This week we started learning basic notions about computers and how they work, from what is a bit and bytes and binary code, as well as how to apply it.

We have been introduced to embedded programming, that is, how to program electronic components to do what we want them to do.

Despite being an engineer, I had no knowledge of electronics, and some very brief knowledge of C++ programming. I had worked with Arduino without understanding anything about what it did, just copying some libraries.

In Barcelona, they explained us different boards with different microcontrollers and we started to program with BArduino.

Barduino 3.0

This is a development board by Barcelona Fab Lab (Fab Lab BCN) for an ESP32 microcontroller together with an ATSAMD11C14A. The main idea of this project is to use the SAMD11 as a Serial bridge to program the ESP32, but being able to program both microcontrollers on one board with the usable pins open for prototyping, that provides an easy way to experiment and prototype new electronic designs.

The main differences between an Arduino and a Barduino are the pin layout and the microcontroller chipset. The Arduino's microcontroller was 'ATmega328P' and the Barduino had an 'ESP32' and 'ATSAMD11C14A' microcontroller. This forced us to download additional boards from the board manager in Arduino IDE in order to communicate with the Barduino. We also downloaded Arduino, which is a software application used to program code on the Arduino microcontroller development boards.

In the following image we can see on the left an Arduino board, and on the right a Barduino board.

Barduino has 2 microcontrollers that we can start to program in our Individual assigment:

1. SAMD 11: it has USB communication, it has micro connections, power, ground, and 2 pins for information.
2. ESP32: it has a lot of memory, wifi, and Bluetooth embedded, but it doesn't know how to talk to the USB.

Individual assigment

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As individual tasks we have had to do several things:

1. Learn to identify the ideas needed in a data sheet.

Here I reviewed the SAMD11 data sheet to better understand what is going on in it.

I had never looked at an integrated circuit data sheet before, so I found it quite tedious. I relied quite a bit on Fab Academy summary documentation to get me started to understand, and then I could go straight to looking at the data sheets. Also, I watched some video tutorial on YouTube on how to go through a datasheet.




2. Learn about Barduino.

As I mentioned, the board I had is the Barduino 3.0 with an ESP32 microcontroller paired with an ATSAMD11C14A that will be used as a serial bridge. This is because the ESP32 does not have the ability to do direct communication, so the SAMD11 will be the translator.




3. Programming the microcontroller SAMD11C14A.

To program the virgin SAMD11 you have to upload the bootloader and configure it as a serial bridge.

First I connected the SWD (Serial Wire Debug) programmer to the Barduino 3.0 and then both to the PC. The SWD programmer is a protocol used to debug and program microcontrollers. Next, I opened the terminal and used the command below to upload the bootloader to the SAMD11.

  		edbg -ebpv -t samd11 -f free_dap_d11c_mini.bin
		

With this step, I am now able to communicate with the SAMD11 through the Arduino IDE.




4. Programming the microcontroller ESP32.

Having the SAMD11 programmed, it can be used as a serial bridge to establish contact with the ESP32 microcontroller.

To do this, turn on (to the left) the small switch on the bottom of the board. This means that the board will boot up in flash mode ready to receive the code, but I had to press the reset button on the top right before uploading the code. Once the code was uploaded, I set the switch to the right and then hit the reset button, then the ESP32 worked.




5. Testing.

For testing, I had to install Arduino IDE and the necessary boards to communicate with the ESP32 and SAMD11.

The following links were copied and pasted into the URLs in the Arduino additional board manager in preferences so that the IDE would find them.

• SAMD11

  		https://raw.githubusercontent.com/qbolsee/ArduinoCore-fab-sam/master/json/package_Fab_SAM_index.json
		

• ESP32

  		https://dl.espressif.com/dl/package_esp32_index.json
		

I started using one of the Arduino examples. A simple one that was to easily control the blinking of an LED. I simply updated the code to map the pin to the correct pin on my board. In SAMD 11 the led pin is number 2.

A detail to take into account in Arduino is that the ON/OFF must be indicated as HIGH/LOW or just 1/0.

In this code, we have 2 functions (usually based on C++ ):

• Void setup(): says that whatever is inside it is executed once, in this case, we are saying that PIN 2 is the OUTPUT, and this information stays forever (until we have a different code sent to SAMD 11).
• Void loop(): which is looping, so it is continuously executing, a function we need to be able to see state changes over time.

void setup () {
	pinMode(2, OUTPUT);
}

void loop() {
	digitalWrite(2, HIGH);
	delay(1000);
	digitalWrite(2,LOW);
	delay(100);
}
	

To also check that the communication with ESP32 was correct, I changed the SAMD11 board to the ESP32 board in the Arduino software, and tried the same example code above.

This time I updated the led pin to 13 (the ESP32's pin) and used a faster blink (100ms).

void setup () {
	pinMode(13, OUTPUT);
}

void loop() {
	digitalWrite(13, HIGH);
	delay(100);
	digitalWrite(13,LOW);
	delay(100);
}
	

Finally, some other assumptions were tried, but all based on very simple codes with the LEDs even at the same time. I need to work more on the programming of these boards in the weeks ahead.

The following video shows how I made the above two codes work together.