Can anyone tell me how I can decrease the inter-character delay on an outgoing serial connection via /dev/ttyS0 on an overo earth with chestnut43 expansion board?  The inter-character delay MUST be below 5ms for successful comms with the device I'm connecting to.  Any help would be much appreciated.

Thanks in advance,
Dave

On Sat, Sep 18, 2010 at 12:45 PM, David Pedersen <signitary@gmail.com> wrote:
I have an application that talks to slot machines using SAS and that has no problems with older machines that use versions of SAS that don't enforce the 5ms inter-character delay specification.  But on newer machines that DO enforce the spec, we're encountering problems because the inter-character delay can be as much as 15ms or more!  We are using the ttyS0 port stubbed out to pins 9 & 10 on the chestnut's 40 pin connector, and then up-converted from 1.8v to 3.3v using a logic level converter and then further up-converted to 5V RS232 spec by an SMD shifter (both from sparkfun.com).  The only information I've been able to glean from Linux forums is to use setserial to set the low_latency flag for INCOMING buffer latency problems, which the angstrom distro doesn't include. Besides I really need OUTGOING latency help, not incoming, although there may be a remote possibility that the flag will do both.

I have also been wondering if the problem could be in hardware, and further wondering if switching to the hardware serial port ttyS1 might solve the problem. I've been having trouble updating my OE installation though, as well as figuring out how to rebuild the u-boot image as indicated in the 2 forum posts that refer to redirecting the ttyS1 port from BT to the 40-pin connector.

Any help would be greatly appreciated.

Dave