Boot loader woes. - Page 5


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Thread: Boot loader woes.54 days old

  1. #41
    Prolific Poster towlerg's Avatar
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    Default Re: Boot loader woes.

    For clarity and for non-bootloader savy peeps could you describe your comms setup. On one end you obviously have a PC's USB port, now does that go to a USB to RS232 converter or to a USB port on the board?

    To echo remarks from John Drew, on most PIC devices if you turn LVP on, MCLR will automatically become active even if the fuse for MCLR is turned off.

    Unless you need to use MCLR as an input, make sure it has a 10k pullup. In some MicroChip documentation they show a cap down to ground as well, I've never bothered. If you haven't already posted a circuit diagram, now might be the time. Also could you post the fuse settings.
    Last edited by towlerg; 16th June 2019 at 13:12.
    George.

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  3. #42
    Junior Member moonshadow's Avatar
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    Default Re: Boot loader woes.

    HI George,

    I have made no declarations at all except for device and Xtal. That was the way it worked seven years ago. I will look into this fuse setting requirement.

    The board is little more than a breakout board with a a power invertor on each port B output. PRogramming path is PC USB socket ..... Pl2303 USB to TTL download cable NOT using it's 5 volt connection , only TX, RX and GND ..... then straight into RC6 and 7.

    I am using a 20 mHz xtal with two 22pf caps and an 18F886, because a Microcode bootloader file exists for it.

    The only other active device on the board is a octal ULN2803A buffer on port B which defaults to outputs ..... with an output state LED indicator on each output. Other loads plug into this.

    The board is powered by a six volt battery pack, with a series 4001 silicon diode. I may increase that to two series diodes on the next prototype and change the programming cable plug to a Pickit style 6 pin plug so that the bootloader file can be programmed on board as well.

    I am sorry for my apparent stupidity but I have brain damage which has wiped out my memory, hence me posting this in the absolute beginners section. jk.

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  5. #43
    Prolific Poster towlerg's Avatar
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    Default Re: Boot loader woes.

    I have made no declarations at all except for device and Xtal. That was the way it worked seven years ago. I will look into this fuse setting requirement.
    That may well be the case, but the compiler and probably the default fuses have changed. From the text of the MicroCode loader it would appear that fuses can be set when loader Hex file is programmed. How did you programme the loader into the PIC device?


    I am sorry for my apparent stupidity
    Please don't think for a moment that anybody thinks you're stupid, the learning curve of this stuff is pretty steep.


    VDD max for a 16F886 is 5.5v so with a fresh battery you're probably over that. A 886 will run on 2.0v - 5.5v

    A USB 2.0 will provide 100mA (and a USB 3 a lot more) of nice regulated 5v, so why not use that? Maybe not such a great idea if there is any chance of a short, so perhaps go with 3 x 1.5V AAA's unregulated.

    I seem to remember you said loopback worked, is that correct?

    What do you currently have connected to MCLR?

    BTW The 886 (and most PIC devices) will sink/source approx 100mA total, so 8 LED with a nice big resistor, say 1K, will be bright enough but not stress either any pin or the whole device. So unless the ULN2803A offers some advantage other than provideing current, you can lose it.

    How do you have the option in the PC programme "Use software reset" set?
    Last edited by towlerg; 16th June 2019 at 16:20.
    George.

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  7. #44
    Junior Member moonshadow's Avatar
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    Default Re: Boot loader woes.

    I took the bootloader from the Proton file and used a PICKIT 3.

    Roger on the supply voltage, that is the reason I wanted to put two diodes in series because new cells measure 1.63 volts and not 1.5 volts, making my 6 volt battery pack ... about 6.5 volts, way out of spec for a PIC.

    The kids board need to be portable and I decided to use a battery pack. They could use the USB 5 volts for development. MAins powered PSU's were ruled out on safety grounds and lack of portability.

    Yes the download cables all survived and all pass the lņopback test, but for other beginners one needsto use the right Com port (as indicated in Control Panel ..... Devices ...... and local echo must be switched off in the terminal program.)..

    ON MCLR I have a 4.7k pull up resistor and a tactile switch to ground. I could have made reset automatic, but decided a manual reset would be better for kids.

    I had about 50 of the ULN2803a which I use a lot of .....

    Exact pinout match for port.B
    500 mA per output.(8).
    UP to 50 volt working for steppers. Built in clamp diodes for inductive loads.
    Cheaper to replace than a PIC.
    Can be paralleled for greater currents.

    HAPPY FATHERS DAY ........... Francis.

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  9. #45
    Prolific Poster towlerg's Avatar
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    Default Re: Boot loader woes.

    Well that all makes sense. If I were you I'd seriously consider the 3 x AAA.

    BTW the Device manager in Control panel is notoriously bad at setting COM ports. Use Control panel to see what COM number is assigned to your USB to TTL serial module, then use what ever app is going to perform comms (in your case MCLoader) to set baud rates.

    Could you fire up your PicKit3 and load the bootloader HEX file. The configuration ie. the fuse setting will be shown in the top half of the program, and tell us what is says.
    George.

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