[Rxtx] Latency Woes

[Curtis Hacker]

I can edit the ECU eeprom to change the baud rate divisor to bump it up 
from 1953, to 15625 or 125000. But as Jim asked how fast the device can 
respond.. not very fast in its stock form.

I can recode a lot of the eeprom for the ecu to alter the ecus baud 
rate, and put the response code into its own interrupt.

I just wanted to make sure that in order to lower latency and increase 
sampling rate. I have to increase the baud rate of the ecu and the user 
right ? Or change the protocol.. to respond with more sensors per request.

On 03/08/11 16:58, jfh at greenhousepc.com wrote:
> Unless the ECU can auto-detect the baud rate, it won't even work.
>
> --
> Julie Haugh
> Senior Design Engineer
> greenHouse Computers, LLC // jfh at greenhousepc.com 
> <http://greenhousepc.com> // greenHousePC on Skype
>
>
>     -------- Original Message --------
>     Subject: Re: [Rxtx] Latency Woes
>     From: Jim Redman <jredman at ergotech.com <mailto:jredman at ergotech.com>>
>     Date: Tue, March 08, 2011 6:40 pm
>     To: rxtx at qbang.org <mailto:rxtx at qbang.org>
>
>     How long does it take the device to generate a response?
>
>     Increasing the baud rate may not help you much if the device takes a
>     significant amount of time to process the request.
>
>
>     On 03/08/2011 04:26 PM, Curtis Hacker wrote:
>     > So if I could get the baud up
>     > 15625, theoretical maximum latency is 1.92ms ? Basically 500
>     samples/sec ?
>     > 125000, theoretical maximum latency is 0.24ms ? Basically 4167
>     samples/sec ?
>     >
>     > Keeping the protocol the same.
>     >
>     > On 03/08/11 15:05, jfh at greenhousepc.com
>     <mailto:jfh at greenhousepc.com> wrote:
>     >> Curtis,
>     >>
>     >> It's nowhere near that bad. I'd measured it once before, and I
>     >> believe it's sub-millisecond.
>     >> --
>     >> Julie Haugh
>     >> Senior Design Engineer
>     >> greenHouse Computers, LLC // jfh at greenhousepc.com
>     <http://greenhousepc.com>
>     >> <http://greenhousepc.com> <http://greenhousepc.com%3E>; //
>     greenHousePC on Skype
>     >>
>     >>
>     >> -------- Original Message --------
>     >> Subject: Re: [Rxtx] Latency Woes
>     >> From: Curtis Hacker <hakcenter at gmail.com
>     <mailto:hakcenter at gmail.com> <mailto:hakcenter at gmail.com>>
>     >> Date: Tue, March 08, 2011 3:27 pm
>     >> To: rxtx at qbang.org <mailto:rxtx at qbang.org> <mailto:rxtx at qbang.org>
>     >>
>     >> Thank you guys, cause I was really worried there. I guess
>     another win
>     >> for math today hahaha. So what is the imposed latency that rxtx
>     has ?
>     >> maybe 5-10ms ?
>     >>
>     >> On 03/08/11 13:14, Bob Jacobsen wrote:
>     >> > On Mar 8, 2011, at 12:33 PM, Curtis Hacker wrote:
>     >> >> Tunerpro log : http://www.ds-map.net/tunerpro_log.csv
>     >> > It's only reading one sensor per line.
>     >> >
>     >> > Note that e.g. Boost PSI changed in lines 6, 30 and 54; every 24
>     >> lines. IAT changed in lines 16 and 40; every 24 lines but at a
>     >> different phase. GramsRev in lines 23 and 47; every 24 lines, at
>     >> yet another phase.
>     >> >
>     >> > Looks like (69-1) readings in 1.30 seconds = 19msec per reading.
>     >> Arithmetic still works!
>     >> >
>     >> > Bob
>     >> > --
>     >> > Bob Jacobsen, LBNL
>     >> > Bob_Jacobsen at lbl.gov <mailto:Bob_Jacobsen at lbl.gov>
>     <mailto:Bob_Jacobsen at lbl.gov>
>     >> +1-510-486-7355 fax +1-510-643-8497 AIM, Skype JacobsenRG
>     >> >
>     >> >
>     >> >
>     >> >
>     >> >
>     >> > _______________________________________________
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>     >> >
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>     >
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>     -- 
>     Jim Redman
>     (505) 662 5156 x85
>     http://www.ergotech.com
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