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USB adapters performance optimization

Posted: Tue Nov 10, 2015 11:38 am
by FORScan
Main advantage of USB adapters against Bluetooth and WiFi ones is performance. But sometimes some optimization is necessary to reach the maximum of possible performance. Below we describe some tricks on how to improve USB adapter speed in FORScan.

FORScan shows some adapter parameters in the Vehicle section:
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Minimum response time is most critical, as it in fact means adapter delay (time added to every request and response). In this case, it is not so bad, but this adapter may work better. Let's try to fix:

1. FTDI UBS 2 RS232 chips by default have odd 16ms delay reading data from buffer. Our luck is that It can be easilty reduced:
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Call Device Manager, find your USB port. (1) Call Properties; (2) Call advanced (3) Change Latency Timer from 16 to 2 or 1 ms.

PC reboot is recommended after this procedure.

This trick works only for FTDI chips. Prolific, Silicon Labs and others have no this latency timer problem.


2. If we check adapter performance now, we will see that minimal response time reduced from 16 to 10 ms:
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Well, it's better but still slow. Another improvement deal is to set the Auto-increase option is FORScan settings:
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Let's check it and re-connect:
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We see great improvement now, FORScan has increased interface speed from 38,4 to 500 Kbps and minimal response time dropped from 10 to 2 ms. This is best reachable delay for china ELM327 USB adapters.

This way is applicable for all USB adapters. You may ask why this nice option is not enabled by default? Answer is simple: initially this option was enabled by default, but it freezes some china adapters, so we have disabled it.

Re: USB adapters performance optimization

Posted: Thu Dec 17, 2015 5:25 pm
by william
Thanks tried this today and got very good improvement.

Re: USB adapters performance optimization

Posted: Tue May 17, 2016 3:23 pm
by Matt1295
followed this guide and worked a treat 13 down to 2/3ms

Re: USB adapters performance optimization

Posted: Thu Jan 12, 2017 4:35 am
by oldbob70
were and how do you find this in the forscan program ?

Re: USB adapters performance optimization

Posted: Thu Jan 12, 2017 4:36 am
by oldbob70
were and how do you find this in the forscan program ?

Re: USB adapters performance optimization

Posted: Thu Jan 12, 2017 4:27 pm
by fred08155
This has to be adjusted in Windows system settings (device manager). FORScan cannot do this for you. You have to do this by yourself.

Re: USB adapters performance optimization

Posted: Thu Mar 22, 2018 4:51 am
by Airborne_Ape
I made a 3min video to walk people through these exact steps:

https://youtu.be/8aRxgeOACEY

Re: USB adapters performance optimization

Posted: Sat Aug 25, 2018 5:16 pm
by d14u
Thank you - found out this myself.

Chinese ELM327 now does 3ms and works like a charm.

Re: USB adapters performance optimization

Posted: Sat Mar 23, 2019 8:34 am
by saeb
For Windows 10

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\FTDIBUS\{Device VID, PID and serial number}\0000\Device Parameters\LatencyTimer

Change from 16 to 2.