[pvrusb2] heat?

[Mike Isely]

On Mon, 10 Apr 2006, Luc Bouchard wrote:

> Michael Roitzsch wrote:
>
>> I have not made any serious measurements, but I have the feeling that
>> when the driver is loaded, the device gets warmer even when unused
>> than without the driver? Is this possible?
>>
>> Michael
>>
>>
>>
>>
> Mine is plugged in 24x7 and is hot to the touch regardless of whether
> the Myth box is running or not.

Actually hot or just warm?  The devices I have are all in a testing 
environment so they're not normally on 24x7.  However I have run a device 
or two for 24 or more hours (idle), and I would classify the temperature 
rise as just "warm".  It is certainly not uncomfortable to touch the 
plastic case, not even close.  In my case I have it sitting on a table in 
the open air.  There are no other heat sources nearby, but there's no 
forced air circulation either.  It's just a normal room in house with 
normal room temperature; I haven't seen any signs to suggest I might have 
to worry about heat.

As for Michael's question: Yes it is possible that the device might draw 
more power (and thus produce more heat) even when idle, after the driver 
is loaded.  The driver does a series of steps to initialize the device and 
this includes sending what amounts to a "power up" command to it.  I have 
to do that in order for the various chips to be initialized by their 
corresponding V4L client modules.  However streaming is not enabled until 
somebody is trying to read video data.  This generally means that the 
cx23416 and the saa7115 (or cx25843 for new hardware) should be idle 
unless you're streaming video - and it is those parts where I would expect 
most of the heat to be generated.  Note that you can tell by inspection 
when streaming is underway because that's when the driver will light up 
the LED on the front of the device.

   -Mike

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