recommendation for 8 port rs232 embedded micro

which baud rate ?

Kasper

What about the AVR FPSLC ? You can add extra UARTs using the on-chip FPGA.

Regards Anton Erasmus

Do the need to be all operational simultaneously?

Depending on the variety of Cypress PSoC you can have up to 4 UART simultaneously, but you can dynamically switch I/O pins so you increas that number to many more if they are not operating simultaneously. If you application does require that all operate simultaneously, if you ar working 1/2 duplex and you can arrange some kind of synchronization, it i possible to split the UARTs into transmitters and receivers and use the pi switching technique as well.

Of course the RS232 will have to be external.

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I have an 8MHz AVR running 4 receiving software uarts and 2 transmitting software uarts. So take a 60MHz ARM thingy and you'll be fine for 8 channels.

Meindert

Be careful with that assumption. AFAIK the AVR can actually toggle pins faster than the Philips LPC2XXX ARM MCU. (If that was the ARM you were referrring too). The speed at which a MCU can toggle an I/O pin has often absolutely nothing to do with the speed at which the same MCU can do other processing.

Regards Anton Erasmus

I designed a multiport comms hub a few years ago which had a mid-range PIC interfaced to a number of '2313 AVRs used as UARTs via SPI. I had to use software SPI on the '2313s; nowadays I'd use the Tiny2313 which has hardware SPI.

Leon

Have a look at the Cypress PSoC Microcontroller. I don't know how many UARTs you can fit into the current devices - but hey're real UARTs - not software ones .....

Richard.

hardware

But the code needed for th uart takes much much more time to execute. That will be the bottleneck IMO.

Meindert

With a bit of thought and care, that should be possible to do in software on a small micro, especially if the environment is not too noisy (so that you can use 4 times oversampling instead of 8 or 16).

How about a Cypress PSoC? If you get one of the larger ones with lots of I/O you should be able to instantiate many UART's. I haven't checked if there is one that can handle 8 but I think the larger ones might. There will certainly be enough I/O. If there are devices that have enough digital blocks for the 8 UART's you'll be set for a one chip solution (for the logic) and a few multi-channel RS232 transceivers.

Cheers,

James.

You say minimal - what sort of thing would the CPU be doing?

Now if you had said 4800 baud right from the start that would of helped a little bit (vs 115,200 baud). I say a little bit because we (the NG) still don't know if that is 8 simultaneous full-duplex channels or a rather mundane 1 of 8 channel mux etc. Yes, based upon the incomplete information an ARM could handle this ok (slow GPIO is not that much of an issue here).

BTW, I would love to help more but even my non-technical customers give me more information than this to go on.

Want specific answers? Supply specific information.

Anchor wrote:

Aha, smells like an NMEA multiplexer :-)

Meindert

Slicing and dicing NMEA data from several simultaneous talkers, repeating the NMEA sentences in an ordered fashion eliminating the collisions.

You guessed it.

If there is no micro that has 8 UARTs operating simultaneously and yo have no desire to create 8 software UARTs, why not try a low end micro an an octal UART, for example

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For the price of one of those octal uarts you can buy 16 ATtinys playing UART, and connect them with SPI.

Meindert

What you need is a reasonably fast micro, and do it all in software. At that slow a baud rate (x8), you could easily do it all in a Ubicom ip2k, running at a leisurely 120 Mips. It would be a one chip solution, unless you need to satisfy the +-12 volt rs232 spec, then you would need external level shifters.

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