Hot!8pin MCU

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naeem1234
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2017/11/20 04:56:21 (permalink)
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8pin MCU

Hello everyone
I am in search of a smallest form factor MCU that has USART serial port in it, even a 4-bit MCU would suffice if it exists.
Can anyone suggest any such MCU? Any help is highly appreciated.
#1

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    qhb
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    Re: 8pin MCU 2017/11/20 05:06:45 (permalink)
    +3 (3)
    There are several.
    Have you looked at 
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    DarioG
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    Re: 8pin MCU 2017/11/20 05:07:01 (permalink)
    +1 (1)
    4bit MCU is so 70s Smile
     
    If you only need to transmit, any PIC will do - in software.
    If you also need to receive, better choose one with a real USART: something like PIC10F302 or alike should work...

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    Ian.M
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    Re: 8pin MCU 2017/11/20 05:15:49 (permalink)
    +3 (3)
    Use MAPS: http://www.microchip.com/maps/microcontroller.aspx
    Select 8 pin in the righthand box for pin count and 1 in the lefthand box for UART ch.  You'll also probably want to uncheck 'Future' under --- Product Status ---.
     
    N.B. MAPS is *****S*L*O*W*****, wait for the page to refresh after every selection or it will forget what you just clicked.

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    #4
    DarioG
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    Re: 8pin MCU 2017/11/20 05:16:39 (permalink)
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    Ian.M
     
    N.B. MAPS is *****S*L*O*W*****,




    "slow" is a placeholder for "idiotic" wink !!

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    qhb
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    Re: 8pin MCU 2017/11/20 05:20:57 (permalink)
    +2 (2)
    DarioG
    If you also need to receive, better choose one with a real USART: something like PIC10F302 or alike should work...

    No such device. Did you mean a PIC10F320? It doesn't have a UART.
     
    According to MAPS, the PIC12F1572 is the cheapest 8 pin option. There is no 6 pin part with a UART.
     
    #6
    DarioG
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    Re: 8pin MCU 2017/11/20 05:43:44 (permalink)
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    Yep, I meant 320 or 322. Strange, I was almost sure that they, and possibly 12F675/683 had a USART - but looks like 12F1571/72 is the smallest available.

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    naeem1234
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    Re: 8pin MCU 2017/11/20 05:50:13 (permalink)
    +1 (1)
    DarioG
    If you also need to receive, better choose one with a real USART: something like PIC10F302 or alike should work...



    Yes i would have to Transmit a code and then wait till i receive it back.. in a forever loop.
    As long as i keep getting the transmitted code back in tact i will have to keep an I/O high, otherwise toggle it low.
     
    That's all.
     
    BTW, USART or UART or real USART.. whats the difference and which is relevant for my application?
    #8
    DarioG
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    Re: 8pin MCU 2017/11/20 06:35:35 (permalink)
    +1 (1)
    If you are doing nothing else, creating a receiver UART in software is doable, especially at low speed (say <=9600)
    So the choice goes in, among size of chip, cost and complexity :)
     
    As for the "name", I seem to remember that uSart was the hardware module that features Synchronous mode too (you can read about it in some datasheet). Otherwise a UART is what is commonly used as a "RS232"

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    naeem1234
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    Re: 8pin MCU 2017/11/20 06:49:27 (permalink)
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    DarioG
    So the choice goes in, among size of chip, cost and complexity :)

     
    So it means that for the simple task as stated above, which is to keep sending a Tx code byte and wait for Rx byte, if Rx=Tx then keep a GPIO pin high else toggle it low.
    It looks like that we can do the above in sw without a uart peripheral. So for lowest cost solution is there any 6-pin MCU also available that can perform above task?
    #10
    DarioG
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    Re: 8pin MCU 2017/11/20 06:52:48 (permalink)
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    I'd say the PIC10F320 or 322 I suggested above.
     
    baud rate?

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    naeem1234
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    Re: 8pin MCU 2017/11/20 07:02:56 (permalink)
    +1 (1)
    baud rate can be slow, few thousand bps would be fine.
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    RISC
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    Re: 8pin MCU 2017/11/20 07:14:28 (permalink)
    +1 (1)
    Hi,
    I recommend PIC16(L)F15313 (8pins) or PIC16(L)F18813 (8pins) because they have on-board EUSART and their internal oscillator is +/-2% from 0 to 60C, which means external XTAL is not needed if your system operates within this temperature range.
    Regards
     
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    rodims
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    Re: 8pin MCU 2017/11/20 07:48:59 (permalink)
    +1 (1)
    naem1234Yes i would have to Transmit a code and then wait till i receive it back.. in a forever loop.
    As long as i keep getting the transmitted code back in tact i will have to keep an I/O high, otherwise toggle it low.

    Sounds like you were implementing a kind of watchdog device. Probably this is only part of a more complex specification, but are you sure you need UART to perform this task ? (at least if you are writing the firmware for the other PIC, too)
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    naeem1234
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    Re: 8pin MCU 2017/11/20 07:59:54 (permalink)
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    rodims
    naem1234Yes i would have to Transmit a code and then wait till i receive it back.. in a forever loop.
    As long as i keep getting the transmitted code back in tact i will have to keep an I/O high, otherwise toggle it low.

    Sounds like you were implementing a kind of watchdog device. Probably this is only part of a more complex specification, but are you sure you need UART to perform this task ? (at least if you are writing the firmware for the other PIC, too)




    Yes you are right it is very much like a watchdog device. The device at the other end has loop back serial interface that i want to make use of to check if its in operation or not.
    What is your suggestion if this can be done in a better way, please give your suggestion.
    #15
    rodims
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    Re: 8pin MCU 2017/11/20 08:10:03 (permalink)
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    No, I have no idea, if you specifically want to test that other devices serial interface.
    I thought you might only want to test whether the other device is alive and can respond to input (like uart).
    (i.e. what does "is in operation" mean ...)
     
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    DarioG
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    Re: 8pin MCU 2017/11/20 08:18:24 (permalink)
    +1 (1)
    IMO this sounds good enough, and a suitable task for a SW UART on that little PIC...

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    Ian.M
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    Re: 8pin MCU 2017/11/20 08:19:02 (permalink)
    +2 (2)
    One of the issues with PICs (and other comparable MCUs) is internal clock oscillator stability over their full temperature range.    e.g. The PIC12F1822 HFINTOSC frequency is +/-2% of nominal for the temperature range 0°C to +65°C, which is acceptable for RS232 comms, which can tolerate a +/-2.6% baud rate error at either end of the link (assuming mid-bit sampling and 8N1 framing), but over its full extended temperature range of -40°C to +125°C, it only guarantees +/-5%.  
     
    You may well need to use a ceramic resonator to clock the MCU accurately enough for error free serial comms over a wide temperature range.

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    rodims
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    Re: 8pin MCU 2017/11/20 08:32:57 (permalink)
    +2 (2)
    DarioIMO this sounds good enough, and a suitable task for a SW UART on that little PIC...

    Yes, actually I just thought, how to keep the idea of a tiny 6 pin PIC (no hardware uart available), if "the smallest form factor" has really top priority.  If 8 pins don't hurt, why not use it ...
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    DarioG
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    Re: 8pin MCU 2017/11/20 08:33:57 (permalink)
    +1 (1)
    Yep, I pointed that out above Smile
    http://www.microchip.com/forums/FindPost/1026032

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