Chaves, Kevin wrote:
> Hi,
>
> So I've been working with an FT2232H chip for about a week now, and libftdi=
> for 2 days. We had an issue with the libMPSSE_spi with linux so I decided =
> to switch to libftdi. I grabbed some source code for using the chip in spi =
> master mode.
What code? From where? Why are you asking libftdi authors instead of
the authors of that code?
> We have two really small issues and I'm wondering if there is a way to conf=
> igure the library to clean up.=20
>
> 1. Clock signal=20
> I think I'm screwed with this one, since its a clock divisor. We need 8Mhz =
> but it seems to jump between 7.5 and 10, going from 7000000 and 8000000 as =
> inputs. I'm guessing I might be able to get it closer but hitting 8 might n=
> ot be possible.
That matches what FTDI AN-108 says.
> 2. Small pauses in the clock..
> Each byte written there is a small pause before the next burst of 8, its ve=
> ry very small but we aren't sure why this is happening. The libMPSSE didn't=
> do this but it also didn't work beyond 50khz... so maybe it wasn't as noti=
> ceable there.
How small is "very very small"? Since's it's synchronous, it
shouldn't matter. If you need a regular clock, maybe you could use an
asynchronous mode.
> 3. Large pause before read
> I think i know why this is happening and there isn't much I can do about it=
> . There is a long pause between writing the command and reading the data. T=
> his likely is because the library I'm using is calling write then read, so =
> its probably more likely having to do with the cpu cycle and driver stack t=
> han it is the chip. But I could be wrong. Our spi device expects to shoot t=
> he data back out immediately.=20
How long is "long pause"?
-jim
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