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Sharing a 4 digit 7 segment display between multiple micrcontrollers

harshit
Expert 1090 points

Hi Team,

I need to interface a display of one system which has a 8 bit micrcontroller and another circuitory. It drives a 4 digit 7 segment display. I now want to drive the same display as and when required using another micrcontroller may be msp430 launchpad series or Tiva controller. So basically I want to share display between controllers.

One thing as per my thinking would be to use buffers in between and control the strobe input by each micrcontroller.

I wanted the reliable method(circuitory) to achieve this. Also the criteria is to realise this with least possible BOM and of course TI pool of components.

Pls find the attached doc for more details....

Regards,

Harshit

7242.Display_sharing_Requirements.pdf

  • 0
    Mastermind 7925 points

    I would add third MCU, something super low end. You can interface all 3 MCUs with i2c, spi or anything you want. 

    There are actually multiple solutions for this task. 

    Regards,
    Maciej 

  • 0
    Guru 46710 points

    Don't share display! Instead build communication channels (SPI, i2c or uart) between slaves and master microcontroller for display data exchange.

  • 0 in reply to Ilmars
    Expert 1090 points

    Ilmars said:

    Don't share display! Instead build communication channels (SPI, i2c or uart) between slaves and master microcontroller for display data exchange.

    Hi..

    Thanks for your reply. Basically the master micrcontroller is already programmed with its own firmware to which I dont have access, nor one wants to redevelop code for it. So communication with the salve msp430 using SPI,I2C or UART was turned down.

    And the only possible option left was to tie down control and data lines from both micrcontrollers to display in such a way that each would be able to display their own data as and when required with low priority for MSP430 microcontroller.Hence buffers was thought bcos one can enable the input data of buffer to appear on outputs by using output enable pin of buffer.This way I can restrict the master control and data lines from driving the display.

    I needed help in building this interface logic using TI components but was confused which be better suitable and yes low cost too. 

    Any idea regarding this or other way to hack the display from master micrcontroller.

    Regards,

    Harshit

  • 0 in reply to harshit
    Guru 46710 points

    harshit said:
    I needed help in building this interface logic using TI components but was confused which be better suitable and yes low cost too.

    Use just msp430 with enough pins, place it "in between" old uC and display. Read display info from "old" microcontroller using port i/o (4 pin interrupts and 8-bit port input), then drive display using other pins. Other chips communicate with your "new display controller" using i2c, spi or uart.

    And yes, this display controller can do lot of other jobs, not only be display controller.

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