AVR-Chat

Mike Harrison wrote:
> 
> You can get away with 5V for RS232, so if your levels ate -5.8 and +6 I would be highly surprised if
> this was the problem, unless your driver IC has delay or risetime issues at lower supply voltages.
> Are the RS232 chips you are using actually designed for 3.3v operation ?


samperi@ampertronics.com.au wrote:
> 
> Is the RS232 (Max 232??) interface chip designed for 3.3V or 5V operation?
> It may have stopped working!!
> 
> Regards
> 
> John Samperi

Al Welch wrote:
> 
> Look at the MAX3228 instead of the MAX232 for lower supply.
> 
> According to Maxim...
> 
> The MAX3228/MAX3229 are +2.5V to +5.5V powered EIA/TIA-232 and V.28/V.24
.
.
.
> Al Welch


The drivers don't seem to be the problem . The STK501 uses a MAX3232 rated at 3.0-5.5v 
to drive the 9-pin J301 connector. My board uses a pair of MAX3244's also rated for
3.0-5.5v. The problem looks like the Dell PCs' +6v threshold.

I guess my real question, for the embedded types on the list, is has anyone else run into
this issue talking to other brands of PC's or is this just a Dell box thing?

As an aside, I noticed that the AVR-JTAG pod didn't seem to have any trouble talking to
my PC even when powered by the system 3.3v, so I opened it up. Low and behold - a boost 
supply shoving 7.3v into a 3-pin 5v linear regulator and a good ol' MAX202 5v only part.
So simple...

Bruce