/*
  Title: blink_led_c.ino
  Author: Lucas Lim
  Date Created: 19/03/2020
  Last Modified: 19/03/2020

  Purpose: Press the switch button to turn on LED
*/

// ----- Preamble ----- //
#include < avr/io.h>       // Defines pins, ports, etc
#include < util/delay.h>   // Functions to waste time, provide the _delay_ms() function

int main(void)

{
  // ----- Inits ----- //
   /*
      DDRx - Data Direction Registers (port x),
      PORTx - Port x data register
      Pinx - Port x input pins address
      Note : Simple way to rememebr PIN=Port INput, PORT= Port Outport Register Thing

      Assignment operators
      To set a bit to one  |= (1 << PinNumber)
      To reset a bit to zero  &= ~(1 << PinNumber)
      To toggle a bit,  ^= (1 << PinNumber)
   */
  DDRB |= (1 << PB2);       // Configure PB2 as output.
  DDRA &= ~(1 << PA7);      // Configure PA7 as input.

  // ----- Event Loop ----- //
  while(1)                  // initialize infinite while loop

  {
    /*
      PORTB |= (1 << PB2);         // Turn on LED pin PB2 in PORTB
      _delay_ms(250);              // delay of 250ms
      PORTB &= ~(1 << PB2);        // Turn off LED pin PB2 in PORTB
      _delay_ms(250);              // delay of 250ms
     */
   // if (PINA & (1 << PA7)) {      // check bit 7 or "PA7" of PORTA is 0 or 1, true if 1, false if 0

   if (bit_is_clear(PINA, PA7)){
      PORTB |= (1 << PB2);          // Turn on LED pin PB2 in PORTB
   }
   else {
      PORTB &= ~(1 << PB2);         // Turn off LED pin PB2 in PORTB
   }

  }                                 // while loop end
}                                   // main end
  

Group Assignment : Comparing the performance and development workflows for other architectures

BBC micro:bit ver 1.3B (ARM microcontroller)

I had borrowed this "BBC micro:bit" board from my instructor, Mr Steven, to test it out over the weekend.

"The BBC micro:bit is a handheld, programmable micro-computer that can be used for all sorts of cool creations, from robots to musical instruments – the possibilities are endless" ~ microbit:website

Microcontroller : Nordic nRF51822 (32-bit ARM Cortex M0)

The microcontroller for the micro:bit is a "Nordic nRF51822 (QFAA model)" by Nordic Semiconductor, measure 6mm x 6mm. It is built around the 32-bit ARM® Cortex™-M0 CPU with 256 KB flash and 32 KB RAM.

Some of the features of this chip are as follow :

Nordic nRF51822

Microcontroller :	32-bit ARM Cortex M0
Program Memory :	256kB Flash
Ram :	32 kB
Oscillators :	- Low power 16MHz crystal and RC oscillators - Ultra low power 32kHz crystal and RC oscillators
Pins :	31 GPIO (General Purpose Input/Output)
Built-in radio :	Bluetooth 4.2 (Multiprotocol 2.4GHz radio)
On-air data rate :	250 kbps, 1 Mbps or 2 Mbps

Architecture :

The ARM Cortex-M family are ARM microprocessor cores which are designed for use in microcontrollers. ~ Wikipedia: ARM Cortex-M

The Nordic nRF51822 microcontroller chip contain the ARM Cortex-M0 32-bit processor.

The Cortex-M0 processor implements the ARMv6-M architecture. Cortex-M0 processor is meant for general use. Unlike the 'ARM11' which is specically meant for smartphone. The Cortex-M0 processor is fully programmable in C and no need to write assembly code.

Inside the Cortex-M0 processor, contain one 'processor' core integrated with other components (like I/O controllers, memory, etc) in the same chip. In other ARM Family, there might contains one or more processor cores. When it is said that the Cortex-M0 processor implements the ARMv6-M architecture, it simply meant that it implement the set of standard as well as optional features as defined in the ARMv6-M architecture.

The ARM Cortex-M0 processor is similar to the AVR microcontroller, it has Flash momory space for program, SRAM momery space for data. In addition, it has its own built-in Flash Programmer.

References :
- Cortex™-M0 Devices : Generic User Guide on infocenter.arm.com

ARM (generic) Archirecture from Wikipedia :
I had searched online for ARM Cortex-M0 datasheet as well as ARMv6-M architecture, but not able to get any official documentation. On ARM website, it require you to register for a 'Developer' account in order to obtain access to the confidential documentation. I decided not to do so, as I am not familiar with this, and I do not want to waste too much of my time. So I referred to a generic ARM Archecture from Wikipedia.

References :
- Wikipedia: ARM architecture

Observations made of the ARM microcontroller

From a beginner point of view and the lack of the actual datasheet for the ARM Cortex M0 MCU, in term of hardware, there are similarity, there the central processor unit, three type of memory, it has Flash memory for uploading of the program, SRAM and the EBI might be similar to EEPROM.

However the three type of memories are neatly arrange side-by-side and supervised by a 'memory controller'. Example the memory controller fetches the program from Falsh and send the data over the databus to the processor and other parts of the circuit. The ARM MCU offer a wide range of features whereby each seperate vendor/manufacturer can choose to implement them or not. Like bluetooth radio, ethernet feature, etc.

The PIOs (pins) are indicated. The primary ones are all with the same configuration. The other PIOs are dependant on what features are implemented...

Programming :

The Nordic nRF51822 microcontroller chip can be program using 'Microsoft MakeCode Editor' or 'micro:bit Online Python Editor'.

micro:bit Online Python Editor runs a version of Python called MicroPython that’s designed to run on small computers like the micro:bit. It’s a full implementation of Python 3 so when you move onto other things (such as programming Python on a Raspberry Pi) you’ll use exactly the same language. ~ micro:bit microphyton docs.

I am using Microsoft 'MakeCode Editor' as it is easier to learn and fast to program the micro:bit using blocks and JavaScript.

1. Plug in micro:bit board using the usb cable provided in the box. The LED status light will lit up and computer will detect the new USB device.



micro:bit usb device detected on the computer as a usb drive

2. Go to Microsoft 'MakeCode Editor' website
https://makecode.microbit.org/

3. Click on "New Project"

4. The MakeCoke User Interface appear.
    On the right side is a simulator to test-run your program
    On the centre column is a list of 'blocks' which you can drag to the right
    On the right column is the 'workspace' where you build your main program
    By default, there will be two 'blocks' in the 'workspace', namely
    - the 'on start' which will run the code when the board is power-up, and
    - the 'forever' block which will run any code placed here in a loop in the background.

5. At the centre column -> Click on the 'Basic' tab -> Drag the 'on button pressed' block into the workspace. This will run code when the button is pressed. By default, 'Button A' is selected for you, you can change to button B if you like.


Dragging the block that involve "Button A" to the right

6. Next place a 'show leds' block inside the 'on button pressed block' and draw an outline of a heart shape. This will display the heart shape when button A is pressed. Then add a 'pause' as well as an empty 'show led' block' below the it.

7. I created a simple program that has the following function :
- When 'Button A' is press, it will display heart (outline) for 3 seconds (which is 3000 miliseconds) and then a blank screen
- When 'Button B' is press, it will display heart (outline) for 3 seconds (which is 3000 miliseconds) and then a blank screen

8. Click the 'Download' button on the bottom left of the editor screen. Specify the location to save the '.hex' file.

9. Once the hex file has downloaded, copy it to your micro:bit just like copying a file to a USB drive. On Windows you can right click and choose "Send To→MICROBIT."

7. Locate the .hex file and drag to the micro:bit drive (mine is drive F). Alternatively, you can right click on the .hex file and choose "Send To→MICROBIT.

8. The led light on the front of the micro:bit will blink as the program is been transfered. Once the program finished downloading, it will run the program automatically.

Programming with Javascript :

Click on 'Javascript' button at the top to go into Javascript editor mode :

Programming with Mu (a Python editor for beginners) :

1. Download Mu ver 1.0.2 from Mu website @ https://codewith.mu/
2. Lauch Mu (Python editor)
3. Click on the " Mode" button and select "micro:bit"

4. Follow the tutorial on this online ebook on microbit micro python
5. In the editor, on line 1 type "from microbit import *" and this will import all the libraries needed for micro:bit
6. I writen the following code

7. Click on the "Flash" button and Mu will automatically transfer the .hex file onto the micro:bit board
8. Press button A and B to try it our. It worked exactly as the program created earlier using 'Microsoft MakeCode Editor'

Review of performance and development workflow :
The hardware features was mentioned earlier above. The micro:bit ARM processor is a much powerful MCU than the ATTiny44A, as it is a 32-bit vs a 8-bit MCU, in addition, the micro:bit is a commerical board with a range of features, so I will focus on the development workflow here and not the hardware aspect.

The development process is very user-friendly and fast. It does not require an external ISP programmer, it has an in-built Flash Programmer, just like the Arduino UNO Rev 3 board. Both boards can be connected to PC/notebook using standard USB cable and uploading of codes is easy and fast. For my ATTiny44A hello world board, it would require an external FabISP and ISP cable(or ribbon) in order to program the board.

'Microsoft MakeCode Editor' for micro:bit is a user friendly development tool, it uses pre-defined building blocks and pieces together to form the main programme. I like the building block concept, it is fast to learn, and fun to use. But this is for beginners. For advance user, you an choose to code in Javascript or Python.

Mu (a Python editor for beginners) for micro:bit is easy to learn and use. The Python programming is similiar to Arduino programming, the codes are simplified and easy to understand, as compared to C programming.

Python programming and Arduino programming are similar, but I find the main difference is that Arduino would require a semi-colon ";" after each line of code, so that Ardunio would known that it is end of the code and it can execute the code first, before reading the next line of code. Python coding do not require a semi-colon at the end of each line of code.

References :
- micro:bit website