On Fri, 10 Jul 2009, Peter C. Wallace wrote:
> Date: Fri, 10 Jul 2009 11:52:00 -0700 (PDT)
> From: Peter C. Wallace <p...@mesanet.com>
> Reply-To: "Enhanced Machine Controller (EMC)"
> <emc-users@lists.sourceforge.net>
> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
> Subject: Re: [Emc-users] Hostmot2 homing
>
> On Fri, 10 Jul 2009, Leslie Newell wrote:
>
>> Date: Fri, 10 Jul 2009 19:29:55 +0100
>> From: Leslie Newell <les.new...@fastmail.co.uk>
>> Reply-To: "Enhanced Machine Controller (EMC)"
>> <emc-users@lists.sourceforge.net>
>> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
>> Subject: Re: [Emc-users] Hostmot2 homing
>>
>> Thanks Peter,
>>
>>> rate sample rate yet, but this could be tried by using the raw-write command
>>> in your HAL init file. With a 5I20, the encoder sample rate is 33 MHz, when
>>> the filter is on, 15 clocks are required to recognize an input (the ~.5 uSec
>>> above) If for example the sample rate were lowered to 3.3 MHz, those 15
>>> clocks
>>> would now be ~5 usec, much better at eliminating PWM interference, and stil
>>> capable are reading encoder inputs up to ~400 KHz
>>
>> How would I go about doing that? I'll start playing with chokes and
>> other filtering first. I prefer to stop noise rather than trying to
>> account for it in firmware. However it would be useful as a fallback plan.
>>
Take a look at the HostMot2 manual page about raw-write and the regmap file.
The sample rate of all encoders in HM2 is controlled by the QFilterRate
register at offset 0x3400. If you set this register to 0x008 you will have 10
times longer filter time constants for all encoders (theres a little
discussion of this in the regmap file). Setting it to 0x800 wil get you back
to 33 MHz sample clock,
Peter Wallace
Mesa Electronics
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