time related weather station - Electrical and Information Technology
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1. Ox2f wait tid printTemp maxminminutei wait tid display 0xc0 wait tid display 1 0x55 wait tid display 1 0x3a wait tid printFloatTemp maxmindu 1 wait tid display 1 Oxdf wait tid display 1 0x43 wait tid display 1 Oxa0 wait tid printTemp maxminhouru wait tid if functionSelect 1 functionSelect 2 display 1 Ox3a wait tid if maxminminuteu 10 display 1 0x30 j else display 1 Ox2f wait tid printTemp maxminminuteu void dispMean Value float meanln float meanOut 22 wait tid display 0x01 wait tid display 1 0x49 wait tid display 1 Ox3a wait tid printFloatTemp meanln 1 wait tid display 1 Oxdf wait tid display 1 0x43 wait tid display Oxc0 wait tid display 1 0x55 wait tid display 1 Ox3a wait tid printFloatTemp meanOut 1 wait tid display 1 Oxdf wait tid display 1 0x43 void normalSituation void wait tid display 0x01 wait tid display 1 0x49 wait tid display 1 Ox3a wait tid printFloatTemp intemp 1 wait tid display 1 Oxdf wait tid display 1 0x43 wait tid display 1 Oxa0 wait tid printTemp hour wait tid display 1 Ox3a wait tid if minute 10 display 1 0x30 wait tid p2. float meanTempOutMon int maxhouri maxminutei minhouri minminutei maxhouru maxminuteu minhouru minminuteu functionSelect int second hour minute day month int nbrOfTemps int nbrOfDays int buttons 10 initiera alla element till 1 int nrButtons antal knapptryckningar sedan senaste lt ENTER gt void wait int time void printTemp int temp void printFloatTemp float temp int precision void dispMaxMinTemp float maxmindi float maxmindu int maxminhouri int maxminminutei int maxminhouru int maxminminuteu void dispMean Value float meanln float meanOut void normalSituation void void decodeDate void float decodeTemp void int decodeChoice void 17 void performFunction void void writeButtonToDisplay int button void init void main tid 50 functionSelect 0 nrButtons 0 nbrOfTemps 0 nbrOfDays 0 meanTempln 0 0 meanTempOut 0 0 meanTempInMon 0 0 meanTempOutMon 0 0 maxtempin 100 0 mintempin 100 0 maxtempout 100 0 mintempout 100 0 maxdi 0 0 mindi 100 0 maxdu 0 0 mindu 100 0 maxmi 0 0 minmi 100 0 maxmu 0 0 minmu 100 0 adin unsigned short int 0x4000 AD 1 adout unsigned short int 0x6000 AD 2 timer unsigned short int 0x8000 display unsigned short int 0xa000 latch unsigned short int Oxc000 encoder unsigned short int Oxe000 display 0x38 wa
3. because of its advantages in making the constructing easier The PALCE22V 10 has 22 pins inputs and 10 outputs Two PALCE22V10 are used in the design The first one decodes the addresses and sets the control signals to the peripheral units i e EPROM SRAM Real Time Clock A D Converter LATCHES and sends the DTACK signal active low I O access to the processor The second PAL sends the control signals to the display and 16 Key Encoder and generates the interrupt signals that are from the Real Time Clock level 5 and the keyboard level 2 The PAL programs can be found in Appendix B Program Memory EPROM 27C128 The EPROM 27C128 is a high performancel28K UV Erasable Electrically Programmable Read Only Memory The program code which controls the construction has been saved in the memory Memory SRAM 6264 The Hitachi HM6264BI is 64k bit static RAM organized 8 kword x 8 bit It is used to save all measure values stack and program variables during the execution It is both readable and writeable Real Time Clock ICM7170 The ICM7170 real time clock is a microprocessor bus compatible peripheral fabricated using Harris silicon gate CMOS LSI process An 8 bit bi directional bus is used for the data I O circuitry The clock is set or read by accessing the 8 internal separately addressable and programmable counters from 1 100 seconds to years An extremely stable oscillator frequency is achieved through the use of a one chip regulated p
4. 1 nbrOfDays meanTempOut nbrOfDays 1 if hour 0 amp amp minute 0 ny dag nbrOfTemps 1 nbrOfDays meanTempln intemp meanTempOut outtemp maxdi intemp mindi intemp maxdu outtemp mindu outtemp maxhouri hour maxminutei minute minhouri hour minminutei minute maxhouru hour maxminuteu minute minhouru hour minminuteu minute if day 1 ny manad nbrOfDays 1 meanTempInMon intemp meanTempOutMon outtemp maxmi intemp minmi intemp maxmu outtemp minmu outtemp maxMonthi month maxDayi day minMonthi month minDayi day maxMonthu month maxDayu day minMonthu month minDayu day else nbrOfTemps wait 10 tid Appendix D Simple user s manual Enter your choice on the keyboard followed by lt ENTER gt 10 11 12 13 Set the program in normal mode i e show the present temperature indoors and outdoors together with the current date and time When started the program is in this mode Show the maximum temperature values of the present day indoors and outdoors together with the actual time Show the minimum temperature values of the present day indoors and outdoors together with the actual time Show the mean temperature values of the present day indoors and outdoors Show the maximum temperature values of the present month indoors and outdoors together with the actual
5. date Show the minimum temperature values of the present month indoors and outdoors together with the actual date Show the mean temperature values of the present month indoors and outdoors Show the maximum temperature borders indoors and outdoors Show the minimum temperature borders indoors and outdoors Enter a new maximum temperature border indoors Enter a new minimum temperature border indoors Enter a new maximum temperature border outdoors Enter a new minimum temperature border outdoors Set the date and time The input format is lt mon mon day day hour hour min min followed by lt ENTER gt 31
6. work properly on the EPROM Improvements Since we got our program to work fine in the test environment we were not too disappointed And since the program worked there it was not altogether bad However there were some things that could have been done better All the work in our program was carried out in the interrupt routines Since interrupts should be handled as fast as possible this was not the best solution It would have been better to set a flag when an interrupt occurred and then check the flag in the unlimited loop in the main program in order to find out what should be done In our project however interrupts occurred rather seldom so we never had any problems with this But if we had written a program where many different kinds of interrupts occurred very often we might have run into problems when using this method Another thing is that we should have written more comments in the program code while writing it in order to make it easier to read Especially the places in the program where we write a lot of instructions to the display and the real time clock are pretty hard to understand afterwards 11 Conclusions During the seven weeks we have learnt how one can design a digital circuit practiced what we have leamt in previous courses especially Design of Digital Circuits Digitalteknik and Computer Organization Datorteknik and improved our knowledge a lot The Digital Project course is perhaps the most inte
7. 0x55 wait tid display 1 0x3a wait tid printFloatTemp outtemp 1 wait tid display 1 Oxdf wait tid display 1 0x43 wait tid display 1 Oxa0 wait tid printTemp day wait tid display 1 0x2f wait tid printTemp month wait tid if intemp gt maxtempin intemp lt mintempin light light 1 if outtemp gt maxtempout outtemp mintempout light light 2 latch light wait tid 28 1 if intemp maxdi maxdi intemp maxhouri hour maxminutei minute if intemp lt mindi mindi intemp minhouri hour minminutei minute if outtemp gt maxdu maxdu outtemp maxhouru hour maxminuteu minute if outtemp mindu mindu outtemp minhouru hour minminuteu minute if intemp maxmi maxmi intemp maxMonthi month maxDayi day j if intemp minmi minmi intemp minMonthi month minDayi day j if outtemp gt maxmu maxmu outtemp maxMonthu month maxDayu day if outtemp lt minmu minmu outtemp minMonthu month minDayu day meanTempln meanTempln nbrOfTemps 1 nbrOfTemps intemp nbrOfTemps meanTempOut meanTempOut nbrOfTemps 1 nbrOfTemps outtemp nbrOfTemps 1 29 meanTempInMon meanTempInMon nbrOfDays 1 nbrOfDays meanTempln nbrOfDays 1 meanTempOutMon meanTempOutMon nbrOfDays
8. 16 aktivt lag EDISP 17 aktivt h g OEKNAPP 18 aktivt lag DTACK2 19 aktivt lag VCC 24 start VPA FCO FCI FC2 AS IPLI INTKNAPP INTTIME IPLO2 INTTIME EDISP A13 A14 A15 A16 DS OEKNAPP A13 A14 A15 A16 AS DTACK2 EDISP OEKNAPP end Appendix C C code os ke ke ake ke ake ak ak ake ok alk ok al af ok ale ake ak af ok ok ke of ae ak ok ak af ake ak ke ok ok ak af ae af ake ak a lk ak oke af ok ak af ak af kak a alk af ok af ake ak af ake a ak ak ok ak af ak af ae ak ak ok test c Detta ar huvudprogrammet som ar skrivet i ANSI C Exekveringen av hela programpaketet borjar i pmain 68k lage main exp4 anropas fran assemblyprogrammet exp4 68k vid avbrott _avben anropar avben 68k vilket tillater avbrott fran PI T ake ake ok ak ke af ake ok ok ke ok al af ok al af ok ak ake ok ak ke ok ak af ake ak af ok a kak ok ak ok ak af ake al a ok ae kak ok al ake ak af ake ok aak ak ak af ok al ake ak a ke ok oaf ak al af ake al ake ak ak ok okok include math h int tid float maxtempin mintempin maxtempout mintempout unsigned short int adin adout display encoder latch timer float intemp outtemp float maxdi float mindi float maxdu float mindu float maxmi float minmi float maxmu float minmu int maxMonthi maxMonthu minMonthi minMonthu maxDayu minDayu maxDayi minDayi float meanTempIn float meanTempOut float meanTempInMon
9. Institution of Information Technology Report of Digital Project Supervisor Bertil Lindvall TIME RELATED WEATHER STATION Project Group 10 Hongwu Tong e98 Ingemar Lind e98 Date 2002 03 01 Abstract This report describes the design process of constructing a time related weather station including both hardware and software A digital circuit has been designed to present the temperatures of indoors and outdoors as a function of the time The circuit will generate an alarm signal if the temperature is beyond a predefined temperature range It can calculate the mean temperature and the maximum or minimum temperature in a day or a month The main part of the hardware is the processor MC68008 with 48 pins which communicates with the peripheral components The programmable logic components PALCE22VI0 are used to generate chip s select signals for different peripheral components and the interrupt signals for the processor The software is written in C and Assembler program language The whole construction has been tested by a development system for MC68008 which can help the designer to debug the hardware and software by using different kind of commands Contents keen COM EN 4 Hardware construccion 5 CGFAPON ENS see en di kane Selten 3 ee ELE 5 PAT PALCE22 VIO EE 5 Program Memory EPROM 27C128 cece ence eee 5 Memory SRAM 62064 6 Real Time Clock ICM7170 eneee 6 A D Converter ADCOSOA nonnen 6 Temperature Sensor
10. LM335 oo XX 6 Display Dot Matrix LCD units onee 6 16 Key Encoder MM T4CO2Z n wa pwe tin mate kab see 6 D TYPE FLIP FLOP SNTAHCT4 SNE eer 7 D TYPE LATCH SN74HC573A nonnen enen 7 Schema construction xeon kn ka kk an n SR e l ke mein EN EN 7 Address MA EE 7 Building and testing the hardware construction 8 SONWALE construcion eneen 2 be eend 9 E EE 11 ri eigene 11 E e EE 12 RE Ten CE vinn la e tat a ane kato keeelie 13 Appendix A Circuit schema nnen 14 Appendix B Program logic eeen 15 Appendix C C code eeen E Appendix D Simple user s manual 31 Introduction The project is an assignment of the course called digital projects The purpose of the course is to illustrate industrial development The project aims towards designing a prototype for further development with necessary documentation The main part of the course consists of designing building and testing the construction The goal of the project is to construct a time related weather station by using a MC68008 processor The specifications are as follows e Two temperatures indoors and outdoors should be measured every one minute and presented together with the date and time e The user should be able to set values for max and min temperatures If the temperature is beyond the temperature range a light diode should be lit as an alarm signal e The station should be able to present the maximum and minimum temperature values on the prese
11. alue meanTempln meanTempOut else if functionSelect 4 dispMaxMinTemp maxmi maxmu maxMonthi maxDayi maxMonthu maxDayu else if functionSelect 5 dispMaxMinTemp minmi minmu minMonthi minDayi minMonthu minDayu else if functionSelect 6 dispMeanValue meanTempInMon meanTempOutMon else if functionSelect 7 dispMeanValue maxtempin maxtempout else if functionSelect 8 dispMeanValue mintempin mintempout else if functionSelect gt 9 amp amp functionSelect lt 13 wait tid display 0x01 wait tid display 1 Ox3e void init void int a int light 0 wait tid a timer 0x10 wait tid intemp adin intemp intemp 123 15 wait tid outtemp adout outtemp outtemp 123 15 wait tid second timer wait tid hour timer 01 wait tid minute timer 02 wait tid month timer 0x04 wait tid day timer 0x05 wait tid if functionSelect 0 wait tid 21 display 0x01 wait tid display 1 0x49 wait tid display 1 Ox3a wait tid printFloatT emp intemp 1 wait tid display 1 Oxdf wait tid display 1 Ox43 wait tid display 1 Oxa0 wait tid printTemp hour wait tid display 1 Ox3a wait tid if minute 10 display 1 0x30 wait tid printTemp minute wait tid display 0xc0 wait tid display 1
12. d funcSelect ar void exp5 void avbrottsprogram timeravbrott init j void wait int time int Lj for i 0 i lt time i for j 0 j lt 100 j 5 void printFloatTemp float temp int precision float t2 t3 int t4 t5 int i int tl int temp t2 temp float t1 if t2 lt 0 0 t2 t2 1 0 for i 0 i lt precision i t2 t2 10 0 t5 int t2 t3 t2 float t5 if t3 gt 0 5 20 t4 t5 l if t4 pow 10 precision t4 0 tl tl 1 j j else t4 t5 printTemp t1 wait tid display 1 Ox2e printTemp t4 void printTemp int temp int t t2 if temp 0 wait tid display 1 Ox2d temp temp 1 t temp 10 t2 temp 10 if t gt 0 printTemp t wait tid display 1 0x30 t2 void dispMaxMinTemp float maxmindi float maxmindu int maxminhouri int maxminminutei int maxminhouru int maxminminuteu wait tid display 0x01 wait tid display 1 0x49 wait tid display 1 Ox3a wait tid 21 printFloatTemp maxmindi 1 wait tid display 1 Oxdf wait tid display 1 0x43 wait tid display 1 Oxa0 wait tid printTemp maxminhouri wait tid if functionSelect 1 functionSelect 2 display 1 0x3a wait tid if maxminminutei lt 10 display 1 0x30 j else display 1
13. d interrupt signal to the processor D TYPE LATCH SN74HC573A While the latch enable LE input is high the 9 outputs respond to the data D inputs When LE is low the outputs are latched to retain the data that was set up If the temperature is beyond the predefined temperature range the processor will generate a signal which goes through the D latch to light the diode Schema construction The whole hardware construction is drawn in the program PAD s Power Logic and the schema can be seen in Appendix A The schema has been improved during the process of the construction From the schema one can see that all units communicate via an 8 bit data bus In order to connect all units data outputs to the data bus it reguires that data outputs have tristate level It means that chips with this functionality cannot affect the signals in the bus until they become active The address bits A12 A0 present the 8192 different bytes within the memory area A13 A16 is used to decode the memory area for different chips When e g the EPROM is accessed the address bus set the address to this unit The PAL decodes that address and activates the control signals to the EPROM and at the same time deactivates the control signals to all the other peripheral units Address map The following figure shows the memory map 0 4000 6000 8000 A000 C000 E000 10000 EPROM A D 1 A D 2 Real Display Latch Encoder SRAM indoors outdoors tim
14. e clock Building and testing the hardware construction The hardware has been built on a board The components are placed in sockets in a good ordering and have mainly been connected to each other by a winding technique A thin cable is winded around the pin of the socket with a tool Some parts mainly the ground and the power pins have been soldered on the board The address bus and data bus have been winded first and then the control signals in order to easily change the connection by debugging because mostly some control signals should be changed After building the hardware it has been tested with a development system called it68 which can help the designer to debug the hardware by using different kind of commands The components have been tested one by one until all components work well Software construction When we had finally managed to get the hardware to work we started with the software development The main programming language used for this was C Some instructions however for example initialising interrupts and setting the stack pointer had to be written in assembler Before starting to write the real program we made a simple sketch of the program flow main method set start values to all parameters write initialization instructions to the display and the real time clock enable interrupts while true unlimited loop wait for interrupts timer interrupt method interrupt
15. it tid display 0x0e wait tid display 0x01 wait tid timer 0x11 Oxlc wait tid timer 0x10 0x10 wait tid 18 init wait tid _avben tillat avbrott while 1 evig loop void exp2 void avbrottsprogram knappavbrott int i fs float temp unsigned short int thebutton encoder 16 wait tid if thebutton lt 15 15 lt ENTER gt if nrButtons lt 9 annars felaktig inmatning buttons nrButtons thebutton spara knapptryckningen nrButtons if functionSelect gt 9 writeButtonToDisplay thebutton else inmatning klar unders k vad som skrivits in if nrButtons lt 9 amp amp nrButtons gt 0 annars felaktig inmatning if functionSelect lt 8 inmatning av funktion fs decodeChoice if fs gt 0 amp amp fs lt 13 functionSelect fs else if functionSelect gt 9 amp amp functionSelect lt 12 inmatning av larmgr ns temp decodeTemp if temp gt 300 0 if functionSelect 9 maxtempin temp else if functionSelect 10 mintempin temp else if functionSelect 11 maxtempout temp else if functionSelect 12 mintempout temp 19 functionSelect 0 T else decodeDate functionSelect 0 T T else functionSelect 0 for i 0 i lt 10 i buttons i 1 nrButtons 0 performFunction utfor olika operationer beroende pa va
16. level 5 read the current temperature outdoors and indoors from the A D converters show the temperatures on the display together with the present date and time if the program is currently in normal mode update the mean temperature during the present day and month if the temperatures are higher lower than the highest lowest temperature of the present day or month save the temperature together with the current time if highest lowest of the day or the current date if highest lowest of the month if the temperature is outside one of the temperature borders set by the user light a warning lamp button interrupt method interrupt level 2 call the button encoder to find out which button the user pressed if the button was not lt ENTER gt save the button in a vector else 11 look in the vector at the buttons recently pressed to find out which 11 function the user desires the entered value of the temperature border or 11 the date and time 11 perform the desired function and update parameters 11 reset the button vector Since the two interrupt methods were the biggest parts of the program we decided to write one each While writing these methods we found out that we could also need some more methods which we also wrote One important method was the wait method When we send instructions to the real time clock or the display we have to wait for a small amount of time bet
17. nt day and in the present month together with the date and time It should also be able to present the mean temperature during the present day and the present month In the first chapter the hardware design is described the software design is described in the second chapter after that the problems are discussed and some conclusions are reached At last there are some appendixes with the schema of the hardware construction and the program code Hardware construction Components The data sheets of the all components used in the project can been found in the information bank on the homepage of the course Processor MC68008 The MC68008 is a member of the M68000 Family of advanced microprocessors It allows the design of cost effective systems using 8 bit data buses while providing the benefits of a 32 bit microprocessor architecture The MC68008 is available in a 48 pin dual in line package and a 52 pin quad plastic package In this project a 48 pin dual in line package is used The MC68008 works in an asynchronous mode in this project It has a 20 bit address bus and an 8 bit data bus PAL PALCE22V10 The designer should decide at which addresses the different peripheral components will be placed Every component needs one or more unique addresses depending on the internal structure In order to reach the goal the programmable logic PALCE22V10 is used to generate the signals that the peripheral components need It is used extensively
18. ower supply It generates periodic interrupt which is used to update the temperature measurement A D Converter ADC0804 The ADC0804 is an 8 bit successive approximation A D converter It converts the analog signal from the temperature sensor to the digital signal It works in free running mode in order to get the measure values quickly Temperature Sensor LM335 In order to measure the temperature below the zero the LM335 calibrated in Kelvin temperature sensor is used in the project It has a breakdown voltage directly proportional to the absolute temperature at 10 mV K Display Dot Matrix LCD units The LCD unit receives character codes 8 bits per character from a microprocessor or microcomputer latches the codes to its display data RAM 80 byte DD RAM for storing 80 characters transforms each character code into a 5 x 7 dot matrix character pattern and displays the characters on its LCD screen 16 Key Encoder MM74C922 This CMOS key encoder provides all the necessary logic to fully encode an array of SPST switches A Data Available output goes to a high level when a valid keyboard entry has been made The Data Available output returns to a low level when the entered key is released D TYPE FLIP FLOP SN74HC74 The SN74HC74 contains two independent D type positive edge triggered flip flops Only one D flip flop is used in the project in order to generate a short pulse signal to the PAL2 which generates further keyboar
19. resting course we have taken during our studying period in LTH 12 References 1 Data sheets in the information bank http www it Ith se it courses Digp datablad datablad index htmo 2 It68 utvecklingssystem for MC68008 http www it lth se digproj PDF files it68 pdf 3 MC68008 8 32 BIT MICROPROCESSOR WITH 8 BIT DATA BUS 4 Brian W Kernigham Dennis M Ritchie The C Programming Language Second Edition Prentice Hall Software Series 13 Appendix A Circuit schema Appendix B Programmable logic PAL 1 device 22v10 CLK A13 A14 A15 A16 AS aktivt lag DS aktivt lag RW 0 skriv 1 las DTACK2 9 aktivt lag GND 12 CSPROM 14 aktivt lag CSRAM 15 aktivt lag CSTIMER 16 aktivt lag ANU P AA ra CSADI 17 aktivt lag CSAD2 18 aktivt lag RD 19 aktivt lag WR 20 aktivt lag DTACK 21 aktivt lag CSLATCH 22 aktivt h g VCC 24 start CSPROM A14 A15 A16 AS CSADI A13 A14 A15 A16 AS CSAD2 A13 A14 A15 A16 AS CSTIMER A13 A14 A15 A16 AS CSLATCH A13 A14 A15 A16 AS CSR AM A13 A14 A15 A16 AS RD RW DS WR RW DS DTACK CSPROM CSRAM CSAD1 CSAD2 CSLATCH CSTIMER DTACK2 end 15 PAL 2 device 22v10 CLK A13 A14 A15 A16 FCO FCI FC2 AS 9 aktivt lag INTKNAPP 10 INTTIME 11 aktivt lag GO J G Lh LA LA mn GND 12 DS 13 VPA 14 aktivt lag IPLO2 15 aktivt lag IPLI
20. rintTemp minute wait tid display 0xc0 wait tid display 1 0x55 wait tid display 1 Ox3a wait tid printFloatT emp outtemp 1 wait tid display 1 Oxdf wait tid display 1 Ox43 wait tid display 1 Oxa0 wait tid printTemp month wait tid display 1 0x2f wait tid printTemp day void decodeDate void int i newmonth newdate newhour newminute for i 0 1 lt nrButtons i if buttons i gt 9 return j if nrButtons 8 newmonth 10 buttons 0 buttons 1 if newmonth gt 12 newdate 10 buttons 2 buttons 3 if newdate gt 31 newhour 10 buttons 4 buttons 5 if newhour 23 return return return newminute 10 buttons 6 buttons 7 if newminute gt 59 24 return tidsstallning samt nollstallning av m tv rden wait tid timer 0x04 newmonth wait tid timer 0x05 newdate wait tid timer 0x01 newhour wait tid timer 0x02 newminute wait tid month newmonth day newdate hour newhour minute newminute nbrOfTemps 0 nbrOfDays 0 maxdi 0 0 mindi 100 0 maxdu 0 0 mindu 100 0 maxmi 0 0 minmi 100 0 maxmu 0 0 minmu 100 0 meanTempln 0 0 meanTempOut 0 0 meanTempInMon 0 0 meanTempOutMon 0 0 int decodeChoice void if nrButtons 0 nrB
21. uttons gt 2 buttons 0 gt 9 buttons 1 gt 3 return 1 else if nrButtons 2 return 10 buttons 0 buttons 1 else return buttons 0 j float decodeTemp void i int 1 25 int komma nrButtons sign 1 float temp 0 0 if buttons 0 12 nrButtons 1 amp amp buttons 0 gt 9 buttons 0 gt 9 amp amp buttons 1 gt 9 return 300 0 for i 1 i nrButtons i if buttons i 12 komma if komma nrButtons komma 1 else return 300 0 else if buttons i gt 9 return 300 0 j if buttons 0 11 minus sign 1 for i 0 i lt nrButtons i if buttons i lt 9 if i lt komma temp pow 10 komma 1 i float buttons i else temp pow 10 komma i float buttons i temp temp sign return temp j void writeButtonToDisplay int button if button lt 9 display 1 0x30 button else button 10 plus display 1 0x2b else if button 11 minus display 1 Ox2d else if button 12 komma display 1 Ox2e j void performFunction void if functionSelect 0 26 normal Situation else if functionSelect 1 dispMaxMinTemp maxdi maxdu maxhouri maxminutei maxhouru maxminuteu else if functionSelect 2 dispMaxMinTemp mindi mindu minhouri minminutei minhouru minminuteu else if functionSelect 3 dispMeanV
22. ween two instructions in order to let the component finish handling the previous one In order to do this we call the wait method which simply goes through some empty for loops Some other methods we added were methods for writing an integer or a float to the display methods for writing indoor and outdoor temperatures to the display together with date and time and methods for decoding the value of the stored buttons in the vector depending on whether they were describing a choice a temperature or date and time An important variable in the program is the functionSelect variable This variable shows which function that has been selected and thereby also in which state the program currently is The three states are the following e Normal mode The program is showing the current temperature date and time on the display When the program is in this mode functionSelect is equal to 0 e Old data mode The program is showing minimum maximum or mean temperature of the present day or month or the selected maximum or minimum temperature borders indoors and outdoors When the program is in this mode functionSelect is between 1 and 8 e Printing mode The user is currently entering a new maximum or minimum temperature border value or setting the time and date When the program is in this mode functionSelect is between 9 and 13 10 Results After about four weeks work we have finished the whole hardware design from
23. writing the design specification selecting components drawing circuit schema building the circuit on the board connecting the different components together testing the hardware and improving it By debugging with the help of the development system we found out that the oscillator didn t work The reason is that the circuit is connected by a winding technique The cable is too long and the components are not soldered on the board so there is noise in the circuit We changed it to an oscillator chip which works well The second problem is that the free running mode connection for the two A Ds should be separately connected to the RESET in order to avoid interaction between the two A Ds After finishing the hardware design we began to design the software which is also an important part in the construction The software development took much less time than the hardware development Within a week we had a program that worked nicely in the testing environment However when we tried to run the program from an EPROM we ran into several problems The first was that our program turned out to be bigger than we had expected and did not fit on the 8x8k EPROM Therefore we had to switch to a 16x8k EPROM This caused some redesign of the hardware and reprogramming of one of our PAL units since the new EPROM took twice as much address space as the old one However the new version soon also worked in the test environment but for some reason it did not
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