can you help me with my project (PIC & temperature sensor & LCD)? [Archive]

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voyage

- 24th May 2011, 14:18

Hi everyone. I'm doing this hobby PIC project, basically it's a thermometer with LCD. I found both a schematics and code (hex file) in some well-known electronics related magazine and i decided to give it a shot. I should add I've never had any experience with uc, especially not PICs. The project didn't seem too difficult and it consists of only 3 IC (a pic, a sensor and DC-DC voltage regulator) , LCD display and a few other usual components. The schematic is attached below.

So i bought all the electronic components, PIC 16f786a and PIC Kit 3 (for programming my PIC). What i've done so far: I programmed my PIC (downloaded the 'hex' file and wrote it into the chip with pickit3) and set the project on a breadboard (protoboard) so that i could test it first. The problem is that it doesn't work. The LCD display doesn't seem to be turned on at all. Now, if i assume that all components are connected correctly (on the breadboard), then I guess the problem might only be in one (or more) of those three parts: PIC (and the code), LCD or the sensor. Like i said, i didn't write the code, but i believe it's written correctly (as i got it from the original author of that project (it was written in MikroBasic)). So checking the code would be the last thing for me to do. I want to check "hardware" parts first. So i decided to test those parts of the circuit, starting with LCD display.

My questions are:

1.) LCD: Any idea where to get a code or hex file for testing my LCD? I basically just want to see if it's working and i need some easy and quick test. Like "hello world" written on display or something. My LCD is 20 x 4 using standard 4-bit interface interface (HD44780 or KS066). Power supply (Vdd) is 5V.

2.) PIC & sensor: The temperature sensor I'm using is a very good one. It has internal ADC, RAM, DSP and it can work in two possible modes. The output temperature is already in digital form (15 bit word). Communicating between PIC and my sensor is via SMBus (very similar to I2C). As you can see on the schematic, the temperature sensor is connected to PIC via 2 pins: SCL (RC3) and SDA (RC4). If i understand correctly, PIC is Master (who provides clock signal) and the sensor is Slave. I checked SCL pin, which is supposed to be 'clock', but on oscilloscope it DOESN'T look like it at all. It's rather a DC signal (around 4,5V; power supply for the sensor, PIC and LCD is 5V) with some noise. So this is surely one of the problems. Any ideas what should I do next?

Any other advices or help would really be appreciated!

Archangel

- 25th May 2011, 09:40

hERE IS A HEX WHICH SHOULD WORK AS YOUR SCHEMATIC IS WIRED
sorry about the all caps

:020000040000FA
:04000000B401EC2833
:08000800F000030E8301BC00AF
:100010000A08B70000308A00FD2898181812181630
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:10006000031DB613B61B0800303E37280408A7004E
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:0A08400037208A0140298A0140296F
:02400E00CA3FA7
:00000001FF

voyage

- 25th May 2011, 09:55

hERE IS A HEX WHICH SHOULD WORK AS YOUR SCHEMATIC IS WIRED
sorry about the all caps
Sorry for asking stupid questions, but... what is this actually? Where did you get it? And how can I use (program) it? Like I said, I'm a total newbie when it comes to PICs and so far I've only ran a few programs (files) from pickit tutorial and played a bit with LEDs on a testing board i got by my pickit3. I also know how to use 'hex' file, but I i have no idea how to use your hex code. Thanks for your answer.

Archangel

- 26th May 2011, 00:19

voyage

- 26th May 2011, 10:59

Intel Hex file is the format which you load into the programmer and gets sent to your pic.
You write your code in P basic and compile it, the compiler translates it into assembly language, then the assembler translates it into Intel hex, which your programmer loads into the PIC.

Where did I get it ? I wrote it last night before bed, I used your LCD defines according to the way your schematic is showing the wiring. It is written for a PIC16F876A operating at 20 mhz, since I could not find any data about a 16F786A I assumed you simply transposed the numbers.

What does it do ?
It simply sends some text to each of 4 lines available to a 4 line LCD
It does not scroll, it puts the text in the same place each time it cycles.

How to use my hex file . . . select all of it by mouse clicking and dragging across it, click copy and then paste into notepad. Save the file with the suffix .hex and the name of your choice, load that into your programmer, I hope it works as I had no time or chip to test it.
I would offer the source code but it would have no value, as it is written in PBasic Pro, and P Basic does not support LCDOUT command (Or so I have been led to believe).

EDIT: And you may already know all I have posted, but the next person coming in and seeing this may not.
Oh, thank you very much! Makes more sense now. Seems like i can test my LCD with this code. I'll try it as soon as i can and i'll get back with the results.

And yes, it is PIC16F876A (i accidently wrote it wrong in my first post) and my crystal is 20Mhz. Btw, mentioning the oscillator (crystal), i heard it can cause some trouble when used on a breadboard (because of all that additional capacitance), so i'll need to test it as well. Without the external oscillator working as it should, the pic won't work and this could be a possible source of my problem too.

jellis00

- 22nd November 2011, 05:55

Like i said, i didn't write the code, but i believe it's written correctly (as i got it from the original author of that project (it was written in MikroBasic)). So checking the code would be the last thing for me to do.

I don't quite understand how you expect to use a PicKit3 to program your PIC when the source code is written in Mikrobasic. How are you going to compile the code? A PicKit3 won't compile for you....all it does is program the PIC from a hex file that has to be produced by a compiler. If you are using PicBasic, you need a PBP compiler from MeLabs.

voyage

- 23rd November 2011, 12:01

I don't quite understand how you expect to use a PicKit3 to program your PIC when the source code is written in Mikrobasic. How are you going to compile the code? A PicKit3 won't compile for you....all it does is program the PIC from a hex file that has to be produced by a compiler. If you are using PicBasic, you need a PBP compiler from MeLabs.
Yes, the source code is in Mikrobasic, but I also have the hex file so all I needed to do was to download it to my PIC and I've done it successfully. It works ok.

Yeah I forgot to tell my project started to work soon after the testing of my LCD and crystal. Still not totally sure what was wrong earlier, but when I replaced my crystal osc with the new one (and move it closer to PIC pins) and played a bit with LCD display contrast, it suddenly started to work. Thanks for your help and suggestions everyone. :)

Acetronics2

- 23rd November 2011, 16:22

Surely it would have been simpler to tell us ...

http://www.elektor.com/magazines/2011/february/contactless-thermometer.1673686.lynkx

ELEKTOR Project IR Thermometer ...
program IR_Thermometer
' * IR_Thermometer
' * Copyright C.TAVERNIER- 2010
' * for Elektor Magazine
' * www.tavernier-c.com (http://www.tavernier-c.com)
' *
' * Microchip PIC16F876A and
' * Melexis MLX90614 IR Thermometer
' LCD module connections
' LCD used in 4 bits mode on Port B
dim LCD_RS as sbit at RB2_bit
LCD_EN as sbit at RB3_bit
LCD_D4 as sbit at RB4_bit
LCD_D5 as sbit at RB5_bit
LCD_D6 as sbit at RB6_bit
LCD_D7 as sbit at RB7_bit
LCD_RS_Direction as sbit at TRISB2_bit
LCD_EN_Direction as sbit at TRISB3_bit
LCD_D4_Direction as sbit at TRISB4_bit
LCD_D5_Direction as sbit at TRISB5_bit
LCD_D6_Direction as sbit at TRISB6_bit
LCD_D7_Direction as sbit at TRISB7_bit
' End LCD module connections
' Variable definitions
dim SensorLow as byte ' Raw temp. low byte
SensorHigh as byte ' Raw temp. high byte
SensorRaw as word ' Raw temp. word
SensorRawCur as word ' Current raw temp.
SensorRawMax as word ' Max. raw temp.
SensorRawMin as word ' Min. raw temp.
Sensor as float ' Real temp (floating point)
SensorString as string[9]
DisplayString as string[9]
PEC as byte ' Control byte (read but not used)
com as byte ' MLX90614 command
PosDecPoint as byte ' Decimal point position
i as byte
' Procedure definition
' Read Temperature From MLX90614
' Input : com specify temp. to read
' Output : raw temp as a word
Sub procedure Read_temp(dim com as byte)
I2C1_Start() ' issue I2C start signal
I2C1_Wr(0x00) ' send address (device address + W)
I2C1_Wr(com) ' send command
I2C1_Repeated_Start() ' issue I2C signal repeated start
I2C1_Wr(0x01) ' send address (device address + R)
SensorLow = I2C1_Rd(1) ' Read temp. low byte (acknowledge)
SensorHigh = I2C1_Rd(1)' Read temp. high byte (acknowledge)
PEC = I2C1_Rd(1) ' Read PEC (not used) (acknowledge)
I2C1_Stop() ' issue I2C stop signal
SensorRaw = SensorLow + (SensorHigh << 8) ' Build temp. word
End sub
' Convert raw data in SensorRaw
' to displayable string in DisplayString
Sub procedure Convert_raw
Sensor = SensorRaw * 0.02 - 273.15 ' Raw temp to Celsius
FloatToStr (Sensor, SensorString) ' Float to string
PosDecPoint = Strchr (SensorString,".") ' Search for dec. point
For i = 0 to PosDecPoint+2 ' Limit display to two digits
DisplayString[i] = SensorString[i] ' after decimal point
Next i
DisplayString[PosDecPoint+3]= ""
DisplayString = DisplayString + " C"

End sub
' Main Program
main:
' Initialize I/O
PORTB = 0
TRISB = 0 ' All PORTB lines as output
ADCON1 = 0x0F ' Configure AN pins as digital I/O
' Initialize LCD display
Lcd_Init() ' Initialize Lcd
Lcd_Cmd(_LCD_CLEAR) ' Clear display
Lcd_Cmd(_LCD_CURSOR_OFF) ' Cursor off
' Initialize Min and Max object temp.
SensorRawMax = 0
SensorRawMin = 0xFFFF
' Initialize SMBus
I2C1_Init(100000) ' I2C/SMBus Clock speed 100 kHz
SETBIT (SSPSTAT,6) ' Force MSSP in SMBus mode
while true
Read_temp (0x06) ' Read ambiant temp.
Convert_raw
Lcd_Out(1,1,"T Amb. : ") ' Write ambiant temp in first row
Lcd_Out(1,10,DisplayString)
Read_temp (0x07) ' Read object temp.
SensorRawCur = SensorRaw ' Make obj. temp. current temp.

If SensorRawCur > SensorRawMax Then ' Is current temp. higher than max. temp.
SensorRawMax = SensorRawCur ' Make max. temp. equal current temp.
End if
If SensorRawCur < SensorRawMin Then ' Is current temp. lower than min. temp.
SensorRawMin = SensorRawCur ' Make min. temp. equal current temp.
End if
Convert_raw
Lcd_Out(2,1,"T Obj. : ") ' Write object temp in second row
Lcd_Out(2,10,DisplayString)

SensorRaw = SensorRawMax
Convert_raw
Lcd_Out(3,1,"T Max. : ") ' Write Max object temp in third row
Lcd_Out(3,10,DisplayString)
SensorRaw = SensorRawMin
Convert_raw
Lcd_Out(4,1,"T Min. : ") ' Write Min object temp in fourth row
Lcd_Out(4,10,DisplayString)
Delay_ms (1000)
wend
end.

IR_Thermometer Fuses for a PIC 16F876A
--------------------------------------
Oscillator : HS
Watchdog Timer : Disabled
Power Up Timer : Disabled
Brown Out Detect : Enabled
Low Voltage Program : Disabled
Data EE Protect : Disabled
In-Circuit Debugger : Disabled
Code Protect : None
FLASH Write Enable : Write Protection Off