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PT100 RTD Evaluation Board

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LemoX
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2009/05/27 08:52:35 (permalink)
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PT100 RTD Evaluation Board

Hi,

Browsing Microchip App. notes I found: PT100 RTD Evaluation Board, I think is a very nice project to lern how to program a USB adquisition systems, but I could not find any source code (embedded or PC), any of you know where to find this code? o is something like a secret (should I pay for this code?).

Thaks

LemoX
#1

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    flubydust
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    RE: PT100 RTD Evaluation Board 2009/05/27 10:18:27 (permalink)
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    Look here http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en026765∂=TMPSNS-RTD1

    Being a little interested in this I looked at the User Guide and I have to say Microchip produce some of the worst circuit diagrams I have ever seen and after struggling to comprehend it the analog circuit design looks like complete garbage. It might be interesting to study the USB side but I hope you don't want to measure temperature with it.


    p.s. I expected the 'firmware' download on that page to contain source but it is just a hex file. Maybe the 'PC software' download includes the firmware source but supplied as a .msi install image I'm not going litter my PC drives and registry with crap just to see what it contains.


    #2
    LemoX
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    RE: PT100 RTD Evaluation Board 2009/05/27 15:27:25 (permalink)
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    Well, I can`t find any source code out there!!! [:o]

    I can't underestand why MCHP does not give us this usefull info [8D]

    LemoX
    #3
    barum
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    RE: PT100 RTD Evaluation Board 2009/05/29 03:37:34 (permalink)
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    I think that Evaluation Boards don't have source. That is difference between them and Demo Boards. Right?


    #4
    xiaofan
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    RE: PT100 RTD Evaluation Board 2009/05/29 07:16:35 (permalink)
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    ORIGINAL: flubydust
    Being a little interested in this I looked at the User Guide and I have to say Microchip produce some of the worst circuit diagrams I have ever seen and after struggling to comprehend it the analog circuit design looks like complete garbage. It might be interesting to study the USB side but I hope you don't want to measure temperature with it.


    Care to share why you consider the analog circuit design looks like complete garbage. Thanks.


    As for the USB side, typically they use HID for communication. Most likely they use similar design like the original PICKit Signal Analysis Source Code.
    http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1960&fragment3_NextRow=16
    http://ww1.microchip.com/downloads/en/DeviceDoc/PICkit%201%20Signal%20Analysis%20V220%20Source.zip

      USB_Links and libusb
    #5
    flubydust
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    RE: PT100 RTD Evaluation Board 2009/05/29 09:52:33 (permalink)
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    ORIGINAL: xiaofan
    Care to share why you consider the analog circuit design looks like complete garbage. Thanks.


    The constant current source for the RTD is generated from a reference voltage VREF from what I thought would be a precision reference till I looked up D1 in the parts list. VREF is generated with respect to ground but the constant current source is proportional to the difference between VREF and VDD. The stability of the constant current in the RTD is actually worse than the stability of VDD. On top of that VDD appears  to be set at about 4.7v but is (optionally) generated from the USB supply which I believe isn't guaranteed to be more than 4.5v so the stability of the constant current source is likely worse than the stability of the 5v supply in the PC + drops in the USB cable etc.

    The 'reference' diode D1 turns out to be a plain 4.3v zener with at least 2mV/C temperature coefficient but if VDD is 4.7v and the zener was 4.3v the zener current with R15 in series is about 10uA which is so far below the knee that the zener voltage will be much less (the diode voltage is specified at 1000 times more current) and likey wildly unstable.

    The really dumb thing is VDD is used for the ADC reference so if the RTD current was proportional to VDD the measurement would be ratiometric. The circuit would work much better if D1 were replaced by a resistor.
    #6
    xiaofan
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    RE: PT100 RTD Evaluation Board 2009/05/30 04:38:18 (permalink)
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    Nice one. I opened the pdf and looked at the schematics for 2 minutes and thought the circuit was about right. But you have looked into the details.

    I added this to the hardware favourites list.
    http://www.microchip.com/forums/tm.aspx?m=358912

      USB_Links and libusb
    #7
    atl95148
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    RE: PT100 RTD Evaluation Board 2010/03/03 16:34:44 (permalink)
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    Please, can anyone or support from from Microchip help me to locate the source code for PT100 RTD Evaluation Board. It mentioned in the manual the source is available. However, the CDROM or web site only has the *.HEX or *.msi file. I think MCHP is really a liar! Supports forks also liar. Without source code, I have not learned anything after purchased the evaluation kit. No source, just the board and few files to download. I have no idea what it does. MCHP please releas the source code.
    #8
    xiaofan
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    RE: PT100 RTD Evaluation Board 2010/03/05 05:16:00 (permalink)
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    ORIGINAL: atl95148
    Please, can anyone or support from from Microchip help me to locate the source code for PT100 RTD Evaluation Board. It mentioned in the manual the source is available. However, the CDROM or web site only has the *.HEX or *.msi file. I think MCHP is really a liar!


    Did you open a ticket in the support website? This is a user forum. For official support, you need to go to the support site and create a ticket.
    http://support.microchip.com

    BTW, where in the user guide does it mention that the source codes are available? I search for "source" in the pdf file and I could not find it. But maybe I did not look hard enough.
    http://ww1.microchip.com/downloads/en/DeviceDoc/51607b.pdf

      USB_Links and libusb
    #9
    atl95148
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    RE: PT100 RTD Evaluation Board 2010/03/05 10:19:42 (permalink)
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    I read the link and manual many many times and visit all the web sites and also search on google.

    It contain same *.HEX and *.MSI file + manual. There is NO source code! Without source code, this board has NO value.

    I waste my monney to purchase it and I should not trust MCHP for its documents or advertisement.
    There is no may I can find out how the RTD data is collected and passing to the PC seamlessly via USB port. I know is possible.

    Please, anyone can help me to find the source code.



    #10
    WaltR
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    RE: PT100 RTD Evaluation Board 2010/03/05 15:03:22 (permalink)
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    Microchip states:

    The PT100 RTD Evaluation Board demonstrates how to bias a Resistive Temperature Detector (RTD) and accurately measure temperature.


    With nothing about demonstrating how the code works.

    #11
    xiaofan
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    RE: PT100 RTD Evaluation Board 2010/03/05 16:07:05 (permalink)
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    ORIGINAL: atl95148
    I read the link and manual many many times and visit all the web sites and also search on google.

    But please point out where Microchip says that the source codes are available.


    It contain same *.HEX and *.MSI file + manual. There is NO source code! Without source code, this board has NO value.

    I waste my money to purchase it


    This may be true for you. So please try to contact Microchip Support and see if they can help you or not. I agree it would be nice to have the source codes.


    and I should not trust MCHP for its documents or advertisement.

    You have to back up the accusation with proof that Microchip documents or advertisement say that the source codes are available.


    Please, anyone can help me to find the source code.


    As I said before, you have to contact Microchip support at support.microchip.com.

      USB_Links and libusb
    #12
    atl95148
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    RE: PT100 RTD Evaluation Board 2010/03/05 17:25:04 (permalink)
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    The User Guide i have is different. I download from Microchip:

    http://ww1.microchip.com/downloads/en/DeviceDoc/51607A.pdf

    In section 2.3.2 it mentions the EXCEL program to read the temperature

    00096R1.xls

    This file was never found on the web site. This is PC source code.

    Other sections: It mentioned:

    This PT100 RTD Evaluation Board Kit includes:
    • The PT100 RTD Evaluation Board (102-00096)
    • PIC18F2550 Firmware (USB)
    • Microsoft Excel-Based GUI
    • PT100 RTD Evaluation Board User’s Guide (DS-51607)
    • Mini-USB Cable

    THis is misleading that there is firmware *.c available - they should only said firmware is HEX file download only!







    #13
    xiaofan
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    RE: PT100 RTD Evaluation Board 2010/03/05 18:47:18 (permalink)
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    ORIGINAL: atl95148
    The User Guide i have is different. I download from Microchip:
    http://ww1.microchip.com/downloads/en/DeviceDoc/51607A.pdf

    I see. That is the first version.


    In section 2.3.2 it mentions the EXCEL program to read the temperature
    00096R1.xls
    This file was never found on the web site. This is PC source code.


    I would not call that PC source codes though. But you might be right that they will show the Excel Macro or VBA codes.
    I sympathize with your situation. So please try to contact Microchip support and report back. I hope they can help you. You might want to refer to this thread as well.


      USB_Links and libusb
    #14
    atl95148
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    RE: PT100 RTD Evaluation Board 2010/03/05 22:27:05 (permalink)
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    I try to contact Microchip support and submit 2 tickets ... still waiting from them.
    Plan to switch using AVR instead. hate PIC micro.
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