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UART Connection suggestions

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pappu_sam

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Hi All,

I want to connect three modules to ARM7 controller through UART.
but ARM7 having only two UART ports.
How to connect the third module to it?
Is it possible to connect three UART modules to ARM7 controller?
IS there any multiplexing of UART ports?

please suggest me......!!!!!
 

shaiko

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If the third input is of voltage levels tolerable by your ARM7, you can implement the extra UART with "bit banging" using the available I/O ports. This is an inefficient solution however...

What is the device you want to talk with on the 3rd UART ?
 

pappu_sam

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@Tahmid

thanks alot for the reply,
what are the digital switches available...
how can we use software to get third UART....please suggest one example....

- - - Updated - - -

@shaiko
thanks for the reply,
the device on third UART will be GPS module....
 

alexxx

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how can we use software to get third UART....please suggest one example....
I have never bit banged UART, but reading a byte could be a bit tricky. There is no clock available like in other protocolls, so you have to be synchronized to read in the center of each bit.
http://www.dnatechindia.com/Tutorial/8051-Tutorial/BIT-BANGING.html
http://electronics.stackexchange.com/questions/11123/bit-banging-a-uart
http://saeedsolutions.blogspot.gr/2012/07/pic12f675-software-uart-bit-banging.html

However, you could multiplex in one UART port, as long as the application scenario allows it.
http://www.alldatasheet.com/datasheet-pdf/pdf/15532/PHILIPS/74HC126.html
http://robosavvy.com/forum/viewtopic.php?t=990&postdays=0&postorder=asc&start=0
 

betwixt

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Actually, as long as you can keep good timing accuracy, bit banged receivers are quite easy. All you have to do is detect the start bit, wait 1.5 bit lengths so you are in the middle of the first data bit and then sample at bit rate for as many bits as there are in the data. It's much trickier if your procesor is doing other things at the same time and you can't guarantee reading at the right moment.

Brian.
 

shaiko

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the device on third UART will be GPS module....
how do you connect it to your MCU?
On PCB?
With a cable?
Is it just for learning/evaluation purposes? or it has to be a well engineered product?
 

Tahmid

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