Forgive my ignorance, but how do I check if the FIFO is enabled?  And, if not enabled, how do I enable it?

On Wed, Sep 22, 2010 at 11:18 PM, R. P. McMurphy <loginreg@gmail.com> wrote:
Have you checked that the FIFO is enabled? I cant imagine any other
reason to have delays between characters. In our system we use a
3.6864Mhz clock with no delays between characters, the 64byte FIFO
works great on both UART1 (ttyS0?) and UART2 (ttyS1?).

On 9/23/10, David Pedersen <signitary@gmail.com> wrote:
> Hi Dave,
>
> Thanks for responding!  To answer your question, we're using 1 start bit, 8
> data bits, a ninth 'wakeup' bit, and 1 stop bit, and are using the CMSPAR
> flag and PARODD to set & clear the wake-up bit.  The first byte we send is
> an address byte, which MUST have the ninth bit set, and any remaining bytes
> in the packet must NOT have the ninth bit set.  All of this works
> perfectly.  Our only trouble is the inter-character delay, which is causing
> the connected device to timeout and cease responding.
>
> My understanding is that the ttyS0 port on the overo is not a true hardware
> port, and I'm wondering if that could be the source of the trouble.  I also
> understand that ttyS1 IS a hardware port, but is redirected to the bluetooth
> subsystem rather than the 40-pin chestnut connector.  I've found Nabble
> posts that indicate the port can be redirected to the 40-pin connector, but
> the information is unclear and seems incomplete.
>
> Bottom line is that I need a way to solve the inter-character delay
> problems, whether by adjusting a setting somewhere, or changing to a
> different port. Do you have any experience with anything like this or know
> of someone who does?
>
> Thanks,
> Dave
>
>
> On Wed, Sep 22, 2010 at 12:08 AM, Dave Hylands <dhylands@gmail.com> wrote:
>
>> Hi David,
>>
>> On Tue, Sep 21, 2010 at 11:52 PM, David Pedersen <signitary@gmail.com>
>> wrote:
>> > We have to write the first byte with a wakeup bit set, basically mark
>> > parity, and then the rest of the message must be sent with space parity.
>> > From 2 or 3 bytes, up to 20 or 30 bytes total in each message.  The
>> > first
>> > byte is being sent independently, then the rest of the stream is sent
>> with a
>> > single write() call, however, surprisingly, the inter-character delay is
>> > greater with the multiple-byte write!  Strange.  We're seeing about
>> 14.5ms
>> > on the single byte, mark parity write, and 15ms delay between the bytes
>> sent
>> > together.
>>
>> Hmmm.
>>
>> Are you sending 7-bit characters with parity? If so, then you may want
>> to configure the uart to send 8-bit characters with no parity and
>> calculate the parity yourself using a lookup table.
>>
>> I'm not familiar with the OMAP UARTs, but all of the UARTs I've worked
>> with will send a FIFO worth of data completely in HW. I guess you
>> might have to look into the driver to figure out what's going on.
>>
>> If you're changing the parity settings, I would expect that it needs
>> to allow the FIFO to drain before changing settings. It's also
>> possible that if the HW doesn't support mark/space parity it might be
>> doing something funky in the driver.
>>
>> It's also possible that the FIFO might not be enabled.
>>
>> --
>> Dave Hylands
>> Shuswap, BC, Canada
>> http://www.DaveHylands.com/
>>
>>
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