Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: Joker94 on December 29, 2009, 09:50:38 PM

Title: No. of UART
Post by: Joker94 on December 29, 2009, 09:50:38 PM

With Uart is it the same as I2C in the way that you can use the same 2 pins for multiple devices.

Or do you need different UART lines for each device.

I hope i have made my point clear.

Joker94

Title: Re: No. of UART
Post by: Razor Concepts on December 29, 2009, 09:52:17 PM

different UART for each device

mega168/mega8 only has 1 uart available, so you can communicate with only one other device

Title: Re: No. of UART
Post by: SmAsH on December 29, 2009, 09:59:28 PM

Although, if you only had to receive from a certain device you could only use rx and gnd.
Same goes from only having to transmit...

Title: Re: No. of UART
Post by: Joker94 on December 29, 2009, 10:11:59 PM

Great

so i could potentially have 2

thanks

Joker94

Title: Re: No. of UART
Post by: frank26080115 on December 29, 2009, 11:29:13 PM

there are many devices i've encountered that have a daisy chain scheme that allows for multiple devices to be connected to a single UART, many of Pololu's products have it, maybe some Dimension Engineering products but I'm not sure.

Title: Re: No. of UART
Post by: Joker94 on December 30, 2009, 12:36:44 AM

Thanks for that info. ;)

Joker94

Title: Re: No. of UART
Post by: Joker94 on December 30, 2009, 01:49:37 AM

on the Atmega 64 on pin 33 and pin 34 there is something i am not sure about.
 it says
Pin 33(WR)
Pin 34(RD)

here is the data sheet.

http://www.futurlec.com.au/Atmel/ATMEGA64.jsp (http://www.futurlec.com.au/Atmel/ATMEGA64.jsp)

is this another UART or a function coincidentaly labled the same.

thanks

Joker94

Title: Re: No. of UART
Post by: rgcustodio on December 30, 2009, 05:15:09 AM

@Joker94
You're reading the specs incorrectly. PG0 and PG1 are designated for PORT G. WR is write strobe. RD is read strobe. ALE is address latch enable. These are all used for accessing external memory/SRAM.

The pins you are trying to locate is PE0 (RXD0) / PE1 (TXD0) and PD2 (RXD1) / PD3 (TXD1). Those are the USARTs that are directly available to you.
Of course if you have extra pins you can do some bit-banging to get more pseudo-serial interfaces.

Title: Re: No. of UART
Post by: Joker94 on December 30, 2009, 06:21:46 AM

thanks rgcustodio

i knew about the others you pointed out i was just not sure if WR and RD were  UART as well

thanks very much

Joker94