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    It should be verified that the MCLR can also be used as an Out. It seems to me that it can only be used as an Input once the MCLR function is disabled.


    To page 144 write: 0 = RB3 is digital I/O

    So I would say that it can be used as In and also as Out


    OK, made the first steps. I would say that the road is long.
    I don't know what volume of oversights you're living with, I think mine are very frequent. In fact the oscillator didn't work because I had put a capacitor of 220 pF and one of 33pF.
    Now at least we're starting to see something.
    As for the MCU, I'd say it's obsolete and doesn't have the functions like today's of an internal oscillator or using the MCLR foot with the digital function. I was just taken by curiosity to other forum and see what happens, but if you really wanted to choose a micro for this function, I think it doesn't take much even with fewer feet and maybe from the enhanced family. The display can be done well with two pins in both I2C and SPI, finding ready-made modules for LCD or with the MAX7219.


    Obsolete or not, you wrote that you use the PIC 16F877A
    and the information that I have indicated to you refers precisely to him.

    Here you will find the Data Sheet

    And on page 184 it is written:
    bit 7 LVP: Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit
    1 = RB3/PGM pin has PGM function; low-voltage programming enabled
    0 = RB3 is digital I/O, HV on MCLR must be used for programming

    You are right about the oscillator, the PIC 16F877A does not have an internal oscillator
    you must necessarily put a quartz or an external RC on it.


    I didn't know the spi LCDs but I ordered i2c modules in China with Ht16k33 able to work with this protocol with better characteristics than the max.
    Possibility to manage 16 at the same time×8 LEDs and quite a few’ of keys and which is good without even creating an anti-bounce because it automatically makes two successive readings at a distance of 20mS before confirming that the key has been pressed. Too bad I won't have them before June. The price of buying at bargain prices.


    thanks for the clarifications. I see the setting for RB3 works because it is currently set as an output to drive a multiplexed display segment.

    to make a SPI driver for parallel LCDs, one is 74xx595. If I'm not mistaken there is the library for Arduino. Then there are clearly also other integrated that can interface or the module with TM1637 which has many options for user interface.
    For the price also in Amazon They are.

    • This reply was modified 2 years, 7 months ago by Picmicro675.
    • This reply was modified 2 years, 7 months ago by Picmicro675.

    I return to the limelight for the last jump.
    In addition to the daily oversights, I connected the module badly and the prototype does not read the load cell. It appears to be in good condition, all the 4 branches measure 1 kOhm c.a.
    I should try with the scheme proposed to me with Op-Amp and see if the strain gauges are still in normal conditions.
    Maybe I should make a Wheatstone bridge with resistors to test if the module is still able to give rational measurements.

    I really appreciate any suggestion.


    Since HX711 modules cost 2 Euro my advice is to buy another one and try if it's the same.
    When I buy such modules I always take two or three and often I find one that has some badly welded component.

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