Re: SPI to RS232 Conversion

On Jul 12, 7:24 am, Joerg <inva...@xxxxxxxxxxxxxxx> wrote:
Artist wrote:
I want to use the MAX9939,
http://datasheets.maxim-ic.com/en/ds/MAX9939.pdf,
on a board with no uP and control it instead with an RS232 serial port
from a PC. I thought at first I could do this with the MAX3110E:
http://datasheets.maxim-ic.com/en/ds/MAX3110E-MAX3111E.pdf
but after reading this spec *** I notice that on both the MAX3110E and
the MAX9939 the SCLK line is an input. Evidently both were meant to
interface to a uP and not each other. How can an SPI peripheral be
controlled from a PC's serial port?

 From the DOS system you can, if the target device is happy with slower
SPI speeds (most are). From a "modern" Windows system I believe
bit-banging isn't truly possible, IIRC the OS is too slow (latency), but
I leave that up to SW experts. It certainly isn't possible with
USB-Parallel adapters but people have sucessfully done it with
PCMCIA-Parallel cards.

Another possibility is the 8 Bits from the National Instruments PCI-6110
card connected to the board the MAX9939 will be on. I see there is no
maximum spec for the tCSS parameter of the SPI bus. Does this mean the
timing of the SCLK does not have to be a regular cycle so all three SPI
lines can be driven by the PCI-6110 digital output lines?

Personally I wouldn't use Maxim chips but that's up to you. May be ok if
no production qties needed. Otherwise check LTC, they've got chips like
this but I don't know if useful to you:

http://cds.linear.com/docs/Data***/12516fa.pdf

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Of course, when is the last time you used a Maxim chip in a design?
Perhaps the problems have cleared up. I noticed a certain VP has
retired, and the replacement has got to be better. The Peter Principle
is real life. So is Dilbert.

Regarding bit-banging, I don't see a latency issue since SPI is all
static logic. When I was at Maxim, we would bit-bang SMB (similar to
i2c) using the cheesy DOS mode of win98 and the parallel port.
However, you could load any number of free versions of DOS these days.
[DrDOS, FreeDOS, OpenDOS]

There was a library that would work in win98 that would allow you do
program the registers of the UART directly, which you could set the
handshake lines. It didn't work in anything more advanced.

One thing to investigate is DOSBOX. It plays old DOS games, something
I never thought could be done. I'm playing Redneck Rampage on X64. It
might have better latency than using a modern windows OS.
.

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