dual uarts

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baftab

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hi
i was working on this project of mine...using at8c51, which has a built in UART, was using it to comm my rfid reader

no i need it to comm it to my pc as well...using serial port
but as 89c51 has one serial port which is already occupied...am confused

i hav heard the there our other uart ics available tht can be interfaced to 89c51

are there???? help please
 

I dont use the 89C series, but it should be possible to write a 'software' UART,
bit switching. I suspect there is an example for the PIC in Nigel's tutorials.

Look here:
https://www.electro-tech-online.com/custompdfs/2007/10/software_uart.pdf

http://www.avocetsystems.com/company/articles/magazine/auart.htm
 
Last edited:
ericgibbs said:
I dont use the 89C series, but it should be possible to write a 'software' UART,
bit switching. I suspect there is an example for the PIC in Nigel's tutorials.
Click to expand...

There is, it's failry trivial to do, and should be for any processor - for those who remember back that far?, the Commodore VIC20 used a software UART - supposedly because they ran out of money to use a hardware one.
 
aright....thanks

but now i think i would need to change my controller as i need more ports...
i miscalculated the requirements before i began working on it

so..tellme about some other controller tht has built in uarts, not one but 2 and more than 4 I/O ports
 
baftab: I've been using the MAX3100 on a project I'm doing... nice hardware UART with FIFO and interrupts. PIC have some CPU's with 2 UARTs, not sure if they have more (a parametric search option on their site will tell you.)

P.
 
baftab said:
out some other controller tht has built in uarts, not one but 2 and more than 4 I/O ports
Click to expand...


The need for 4 hardware UART's is a little over kill for most applications heh. I would suggest you have a look at using a higher language so that software UART is as easy as;

Code: 
Include "SUART.bas"

SUART.SetBaudrate = sbr9600

Data = 0
While True
     Inc(Data)                         // Increment the data regiester
     SUART.SetTX = PORTB.0
     SUART.WriteByte(Data)
     SUART.SetTX = PORTB.1
     SUART.WriteByte(Data)
     SUART.SetTX = PORTB.2
     SUART.WriteByte(Data)
     SUART.SetTX = PORTB.3
     SUART.WriteByte(Data)
     DelaymS(50)
Wend
 
A note on that though - be sure to setup the default condition of all your SUART pins depending on what mode you choose (Inverted/True) or the first piece of data to be received will be corrupted (but then the software will leave it in its correct "idle" state)
 
baftab said:
you hav interfaced max3100 with 89c51??
or some other controller?
Click to expand...

I used a PIC processor, but the MAX3100 has a simple SPI interface which will work with almost any microcontroller, even if it does not have a hardware SPI port, because SPI is easy to do in software and is *not* timing-constrained as software UARTs which need precise timing loops.

Hope this helps,
P.
 
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