FPGA Climatic Oana Valentina Rusu Advisor: Lecturer eng. Adrian-Vasile Duka PhD “Petru Maior” University of Tirgu Mures, Romania

Contents Introduction Project overview HDL Design Software Design Conclusions Demo

Introduction It is a climate control platform based on FPGA. Replaces the two devices used to control the heating and cooling system ( the thermostat and the AC remote control ) All available commands and menus are shown on a screen.

Why this project? Learn something new. Discover the usage and capabilities of an FPGA starting from simple to complex projects. Designing an useful platform for everyday use.

System Specification Allows to read temperature; Current temperature is displayed on a 7segment display; Allows to control the heating and cooling systems; It has an improved user interface ( it displays an interactive menu on the screen ); Commands are sent through a remote control; The controlling algorithms and the menu design were implemented on an integrated soft core;

Project overview

This project is divided in two parts:

HDL Design System architecture: AHB_Lite_SoC - the SoC based on the AHB-Lite protocol (implements the control logic, user interface etc.) IRReceiver - decodes the remote control signal and encodes the desired keys; PmodTMP - converts and reads the temperature from the temperature sensor; temp_7seg_display - displays the temperature on a 7 segment display; PWM – generates the PWM control signal;

PmodTMP module 3-wire digital thermometer and thermostat; 12 bit resolution In our case : displays positive temperatures, with one decimal part ;

PModTmp State Machine

IR Receiver Module Reads the signal from a TSOP kHz IR receiver; Decodes the remote control signals ( NEC format ) and assigns them a 4-biy key; Key NameAddress CodeData CodeValue Assigned On/Off (0111) A (0001) B (0010) C (0011) O (0101) Up (0110) Down (0100) Left (1000) Right (1001)

IR Receiver State Machine

PWM Module generates a PWM signal for the cooling system; duty cycle depends on the value received from the PID controller ( e.g % duty cycle, 63 – 100% duty -cycle); 1 ms period;

Temp_7seg_display module Shows the current temperature on a 7segment display;

Bin2bcd logic

AHB- Lite Protocol It is used in SoC designs as the on-chip bus. It is a subset of AHB protocol defined in the AMBA 3 standard; It simplifies the design for a bus with a single master; Main components: master component, slave components, address decoder, multiplexor;

The AHB-Lite SoC

AHB-Lite Master: Cortex M0 Design Start Based on a simplified version of the ARM Cortex M0 processor; It has a NVIC Interrupt controller with 16 Interrupt lines; Supports 16 and 32 bit instructions; Microcontroller-oriented processor for MCU and SoC applications;

AHB-Lite Slaves – AHB2CTRL AHB2CTRL - slave module which receives data from the master module : HCLK or negedge HRESETn) begin if(!HRESETn) rCTRL <= 8'b0000_0000; else if(rHSEL & rHWRITE & rHTRANS[1]) rCTRL <= HWDATA[7:0]; and assigns it to the output wires: assign CTRL = rCTRL;

AHB-Lite Slaves - AHBINPUT AHBINPUTS - slave module which reads data from inputs : HCLK, negedge HRESETn) begin if(!HRESETn) input_data <= 16'h0000; else input_data <= INPUTSIN; end and it sends to the master: assign HRDATA[15:0]=input_data; Input data:  irq_remote – irq signal,  remote_code[3:0] - data,  temperature[7:0]

AHB-Lite Slaves – VGA Controller Modifications: Invisible cursor; Custom cursor repositioning – for clear_screen() function; Modifying screen tiles and color text;

clear_screen() function When the 13 th ASCII character is displayed -> cursor repositioned to initial position (0,0); The vga memory will be “rewritten” with empty characters; Cursor repositioning after displaying again the 13 th character; void clear_screen(){ printf("%c",13); for(i=0;i<8;i++) printf(" "); printf("%c",13); }

Software Design The software component is written in ANSI C and ARM Assembly. The project itself contains 4 files: CM0-DS.h – contains the peripheral memory map ; retarget.c – contains the implementation of functions used to display the text; cm0dsasm.s – contains instructions which handle the interrupt vector; MyProgram.c - contains the code used for menu display and control algorithms;

Interrupt Controller NVIC ( Nested Vector Interrupt Controller ) which is tightly coupled with processor core; 16 prioritized interrupts supported;

Interrupt Handling We have to write a handler for each interrupt line from the handler vector: Input_HandlerPROC EXPORT Input_Handler IMPORT INPUT_ISR PUSH {R0,LR} BL INPUT_ISR POP {R0,PC} ENDP

Heating Algorithm Three States:  Active heating – turns the heating system on if current temperature is lower than the setpoint;  Pause heating – turns the heating system off and jumps to active state if current temperature is lower with x degrees than the setpoint;  Exit heating – returns to main menu;

Heating Algorithm

Cooling Algorithm Three States:  Active cooling– turns the cooling system on if current temperature is higher than the setpoint;  Pause heating – turns the cooling system off and jumps to active state if current temperature is higher with x degrees than the setpoint;  Exit heating – returns to main menu; The cooling algorithm includes a PID controller.

Cooling algorithm

PID Controller a control loop feedback mechanism widely used in industrial control systems; used to control fan speed ; PID coefficients were determined experimentally ( manual tuning );

Wiring scheme

Conclusions The following goals have been achieved: Learning Verilog basics; Integrate ARM Cortex M0 Design Start IP core and creating a custom AHB-Lite SoC system with peripherals; Developing other Verilog specific modules ( for temperature measuring and display, IR decode, PWM signal generation); Developing clear_screen() function for C software; Creating the cooling/heating algorithms in C; Handling custom interrupt in Verilog and Assembly; Developing interactive user interface in C; Hardware component design and assembling ; Other improvements ;

Future considerations Controlling from distance through an internet connection ( we will use a raspberry pi as a web server, it would be more efficient ); Extend the design to Intelligent House Project.

Demo

Thank you for your interest!