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* SNR calculation in stv0299 driver
@ 2005-07-19 16:08 Gill Robles-Thome
  2005-07-19 16:08 ` Gill Robles-Thome
  2005-07-19 16:28 ` Ralf Baechle
  0 siblings, 2 replies; 3+ messages in thread
From: Gill Robles-Thome @ 2005-07-19 16:08 UTC (permalink / raw)
  To: linux-mips

Hi -

Can anyone explain the algorithm used to calculate the SNR for the
stv0299 driver? Ie


	case FE_READ_SNR:
	{
		s32 snr = 0xffff - ((stv0299_readreg (i2c, 0x24) << 8)
				   | stv0299_readreg (i2c, 0x25));
		snr = 3 * (snr - 0xa100);
		*((u16*) arg) = (snr > 0xffff) ? 0xffff :
				(snr < 0) ? 0 : snr;
		break;
	}
 

I don't understand where the 0xa100 value comes from, or why the result
is them multiplied by 3!  Registers 0x24 and 0x25 are apparently "Noise
Indicator" registers, but the stv0299 specification doesn't explain very
well how these registers should be used.

Thanks for your help,
Gill

^ permalink raw reply	[flat|nested] 3+ messages in thread
* SNR calculation in stv0299 driver
  2005-07-19 16:08 SNR calculation in stv0299 driver Gill Robles-Thome
@ 2005-07-19 16:08 ` Gill Robles-Thome
  2005-07-19 16:28 ` Ralf Baechle
  1 sibling, 0 replies; 3+ messages in thread
From: Gill Robles-Thome @ 2005-07-19 16:08 UTC (permalink / raw)
  To: linux-mips

Hi -

Can anyone explain the algorithm used to calculate the SNR for the
stv0299 driver? Ie


	case FE_READ_SNR:
	{
		s32 snr = 0xffff - ((stv0299_readreg (i2c, 0x24) << 8)
				   | stv0299_readreg (i2c, 0x25));
		snr = 3 * (snr - 0xa100);
		*((u16*) arg) = (snr > 0xffff) ? 0xffff :
				(snr < 0) ? 0 : snr;
		break;
	}
 

I don't understand where the 0xa100 value comes from, or why the result
is them multiplied by 3!  Registers 0x24 and 0x25 are apparently "Noise
Indicator" registers, but the stv0299 specification doesn't explain very
well how these registers should be used.

Thanks for your help,
Gill

^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: SNR calculation in stv0299 driver
  2005-07-19 16:08 SNR calculation in stv0299 driver Gill Robles-Thome
  2005-07-19 16:08 ` Gill Robles-Thome
@ 2005-07-19 16:28 ` Ralf Baechle
  1 sibling, 0 replies; 3+ messages in thread
From: Ralf Baechle @ 2005-07-19 16:28 UTC (permalink / raw)
  To: Gill Robles-Thome; +Cc: linux-mips

On Tue, Jul 19, 2005 at 05:08:10PM +0100, Gill Robles-Thome wrote:

> Can anyone explain the algorithm used to calculate the SNR for the
> stv0299 driver? Ie

You may want to post such questions to a list that's actually related
such as the Linux TV list, see your friendly MAINTAINERS file.

  Ralf

^ permalink raw reply	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2005-07-19 16:43 UTC | newest]

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2005-07-19 16:08 SNR calculation in stv0299 driver Gill Robles-Thome
2005-07-19 16:08 ` Gill Robles-Thome
2005-07-19 16:28 ` Ralf Baechle

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