Single I/O for 16x2 LCD

[garg29]

hi friends,
i am facing a problem.......i have to interface a 16x2 lcd with microcontroller but the problem is i'm having only one I/O left, remaining are bieng used for some other purpose(which i cannot change) can someone please guide me how can i handle the situation?

Thanks

Regards,
Garg

 

[neelandan]

Use this as an output for the E (enable) input of the LCD. Wire the R/W line low (do not read from the LCD).

Next comes the hard part: you will have to find four lines to use as data - reuse some inputs or multiplex some outputs.

Otherwise, there are some solutions to use two lines to control LCD - try searching for LCD two IO

 

[mezo]

In this case you will have to buy a serial LCD

 

[garg29]

Thanks for replying friends.
is there a chance of success if i use some small microcontroller on lcd end & communicate with main Microcontroller through "1-Wire Communication"?

regards,
Garg

 

[FvM]

The most obvious solution, not requiring a special protocol, would be an UART, most likely a software TXD UART at the host processory. Alternatively, you can use something similar to Maxim-Dallas 1-Wire protocol (including a possible emulation of the original protocol). That's feasible e. g. with a small PIC.

 

[garg29]

Thanks a lot FvM. I think i'll have to go for "Maxim-Dallas 1-Wire protocol" coz i don't even have TXD UART pin free coz the system is communicating with PC through RS232.
I hope for success.

Thanks,

Regards,
Garg

 

[umery2k75]

You could use Shift register and hook up with some other discrete logic gate. that you could sent 8 bits of data and other data for R/W and other things necessary for LCD. You could use IC like 74164 or any other serial to parllel converter with output enable must.You need an adder circuit that will be counting the number of bits output on the PIN. Once you reached like 11 bits or 10. Whenever you get required bits that will be used by the LCD then you output it, then all the lines would go on to the LCD and you can use it.Your last bit will enable the output of all and there by LCD will see it as a parallel data.Repeat this cycle and would LCD works great with no doubt.

 

[bobcat1]

Hi

Looks at EDN site from last month on the design ide section there was an application on how to use single IO to drive LCD display from a micro controller all though the hardware is a bit compliceted it can be done

All the best

Bobi