UPC EETAC Bachelor's Degree in Telecommunications Systems and in Network Engineering EEL

 

Blink_LED using FSM control flow and MCC Melody

MCC 
1. Specifications Planning Dev. & test Prototype Report

Let us design A LED blinker using the MPLAB Code Configurator MCC Melody.

The final idea left for this third tutorial is to control the program flow using a FSM pattern, as we do in CSD. Reference from Microchip University on this idea.

 

NOTE: Other versions of the same project:

Blink_LED: Using PIC18F and bare-metal register configuration in C language

Blink_LED: Using Arduino. DEE LAB5 Project #2.

Thus, you can compare and see what is different accordingly to the technology selected. For instance, in Arduino we have to use timing functions (millis() or micros() ) to generate the var_CLK_flag on polling, while here we have configured directly one of the timer peripherals to trigger real-time interrupts. 

Symbol and waveforms.

 Symbol and waveforms

Fig 1. Blink_LED_FSM symbol and state diagram.

 

Specifications 2. Planning Dev. & test Prototype  Report

A) Planning hardware

 

Blink_LED_FSM schematic

Fig 2. Blink_LED_FSM PIC18F46K22 connections.

 

B) Planning software

To define a FSM, we have two options, and thus you can compare their features:

FSM style B from Microchip University courses. Learn how to install the FSM structure from this guide on FSM design pattern.

We will start using Style A as in CSD. As shown in the state diagram, outputs at each state are represented in parenthesis and coloured red.

State diagram

Fig 3. State diagram.

 

Specifications Planning 3. Dev. & 4. test Prototype Report

A) Developing hardware

We can use some elements of the CSD_PICstick board modelled in Proteus as the hardware platform where to check our circuit.

 

Fig 4. Circuit captured in Proteus modelling the CSD_PICstick board.

 

B) Developing software

The blinking timing resource is based on TMR0. N1 and N3 are configured in the MCC window. N2 will adopt two values to be selected with the switch P:

N2 values

Setting the CLK times is solved applying the MCC-generated driver functions, as shown below:

 Start_CLK state

The full project "Blink_LED_FSM.zip".

Use Proteus simulations or download the application to the CSD_PICstick.

Measure the signal W period TW. Why the frequency is lower than 200 Hz when selected? Solve the same project using bare-metal style and compare these features.

 

C) Step-by-step testing

 

Specifications Planning Dev. & Test 5. Prototype Report

 

Specifications Planning Dev. & Test Prototype 6. Report

 

 

 

Blink_LED with debounced ST_L button

MCC 

We can use this FSM Debouncing_Filter to clean the noise signal from the ST/SP push-button.

Now, the system responds to the ST_L click using the var_ST_debounced variable that is set only after the push-button signal is filtered. On the next state Start_CLK, while setting up the blinking CLK, the signal var_ST_ack is send to the debouncer, so that it can be initialised once the user has released the button.

Blinking LEd debounced

Fig 1. Modified Blinking_LED_FSM state diagram.

We can use the same timing resource, such TMR0 for both FSM, or better, we can assign to each FSM a different timer, one for generating the blinking waveforms, and the other for sampling the ST_L while debouncing. MCC will facilitate such hardware adaptations.

 

Fig 2. Hardware-software diagram to visualise the location of each FSM and the complete system.