spi and rs232

[CTzar]

What's the easiest (and cheapest) way to communicate with a SLAVE spi device (cs5531 to be exact) via rs232? Any way this can be done without a microcontroller? Is it possible to connect two slave spi devices together (the MAX3110 sure looks good if this can be done).

And please let me know if this is the wrong forum (I'm quite new here).

TIA

c-tzar@c-tzar.com

 

[Lewish]

You don't want RS-232. That is a computer protocol for external devices. SPI is a 3 wire link. Ground, clock, and data. You can connect 2 devices together as long as one is a master. But, most likely, you are going to want to use a microcontroller to arrange and control the data stream with it pieces, and to control the clock line.

 

[CTzar]

Hmmmm, suppose I should have been more specific. =) I want to communicate with the A/D converter throught the rs232 serial port of my PC with as little circuitry/programming as possible. (REALLY don't want to use a microprocessor if it can be helped at all)

 

[Lewish]

What is your application? How many of these are you going to build? What A/D converter?

More info = more help!

 

[beyersk]

Hi CTzar

The easiest would probably be if you use a Maxim-Dallas 1-wire A/D converter like the DS2450 which has 4 channels at 16 bit resolution. Dallas does supply a device that you may plug into your serial com port on the PC to communicate with their 1-wire devices. The internet site of Maxim-Dallas is:

http://www.maxim-ic.com

There is also appnotes available from them on how to do this if you are interested in building your own.

Regards
Beyers

 

[CTzar]

First of all, I appreciate all of the responses. =D

The application is simply a loadcell (measures weight/force) hooked up to an A/D converter from which I want to read the raw counts (digital data) via the serial port on a PC. Loadcells put out voltages that typically range from 0-30mV at most so I'll need an A/D that's pretty sensitive and has flexible gain settings. I also want a differential inputs. Four channels would be nice but it not absolutely necessary. It would also be really nice to avoid surface mount, but if I can't, oh well, I can deal.

The CS5531/32/33/34 claims to be designed for this type of application and seems perfect for the job if only I could find an easy way to communicate with it.

The 1-wire to rs232 adaptor/DS2450 combo looks nice for some apps, but it just doesn't look like it will cut it for loadcells. It looks like the minimum full scale voltage for this chip is 1.60V and I'll probably never go over 30mV getting less than 20% of the full scale.

Any other chips out there sound like they might fit the bill?

 

[beyersk]

You would definately have to use a amplifier if the signal is only 0-30mV, also the diff input means you also need an instrumentation amplifier to handle that. Thus, it realy seems you need a complete designed system.

Look at PC Data Acquisition Cards or something like the ADAM modules. Go to

http://www.promicro.co.za/promicro.htm

and go to their Industrial Automation Products where you will find a good idea of what is available.