[Bluez-devel] RSSI value in floating point

[Bluez-devel] RSSI value in floating point

[Khairulmizam Samsudin]

Hi,

I have inspect bluez-libs codes and seems that some modification can 
make it happen. However, would the devices it self return RSSI in 
floating point?

regards
xource

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Re: [Bluez-devel] RSSI value in floating point

[Marcel Holtmann]

Hi,

> I have inspect bluez-libs codes and seems that some modification can 
> make it happen. However, would the devices it self return RSSI in 
> floating point?

simple answer is no. The RSSI is a signed integer.

Regards

Marcel



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Re: [Bluez-devel] RSSI value in floating point

[Khairulmizam Samsudin]

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Re: [Bluez-devel] RSSI value in floating point

[Andrew Kohlsmith (lists)]

On June 21, 2008 09:59:28 pm Khairulmizam Samsudin wrote:
>  1. Thanks. That saved me a lot of time
>  2. Assuming that I purchase a development kit. Would it be possible to
> modify bluetooth stack to achieve the objective?

Why?  Is it so difficult to say floatrssi = (float)intrssi/(float)INT_MAX?

-A.

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Re: [Bluez-devel] RSSI value in floating point

[Marcel Holtmann]

Hi Andrew,

> >  1. Thanks. That saved me a lot of time
> >  2. Assuming that I purchase a development kit. Would it be possible to
> > modify bluetooth stack to achieve the objective?
> 
> Why?  Is it so difficult to say floatrssi = (float)intrssi/(float)INT_MAX?

so and that gives you anything because? The hardware returns a signed
integer and converting that into float is useless.

Also the RSSI value retrieved from an already established connection is
different than the one you get during inquiry.

Regards

Marcel



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Re: [Bluez-devel] RSSI value in floating point

[David Stockwell]

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The constraint is actually in the Bluetooth Specification, which specifies that RSSI is a single signed octet (byte) with a range of -127 to +127 in dB.  I have attached a screenshot of the section for you.

If you wish, you can return the signed integer returned from BlueZ and convert it yourself to a float, but recognize that the underlying value is an integer.

If you have not done so already, suggest you get a copy of the Bluetooth specification, which describes the BT protocol and stack in detail.  The specification is available from the Bluetooth SIG, at http://www.bluetooth.org/ 

Best regards,

David Stockwell
  ----- Original Message ----- 
  From: Khairulmizam Samsudin 
  To: BlueZ development 
  Sent: Saturday, June 21, 2008 8:59 PM
  Subject: Re: [Bluez-devel] RSSI value in floating point


  1. Thanks. That saved me a lot of time
  2. Assuming that I purchase a development kit. Would it be possible to modify bluetooth stack to achieve the objective?

  Regards
  xource

  Marcel Holtmann wrote: 
Hi,

  I have inspect bluez-libs codes and seems that some modification can 
make it happen. However, would the devices it self return RSSI in 
floating point?
    
simple answer is no. The RSSI is a signed integer.

Regards

Marcel



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Re: [Bluez-devel] RSSI value in floating point

[Andrew Kohlsmith (lists)]

On June 22, 2008 06:07:38 pm Marcel Holtmann wrote:
> so and that gives you anything because? The hardware returns a signed
> integer and converting that into float is useless.

I did not say it would be any more useful; I merely asked him why he can't 
convert it to float on his own instead of demanding the stack do it.

> Also the RSSI value retrieved from an already established connection is
> different than the one you get during inquiry.

Interesting; is the RF PA AGC set differently during inquiry?

-A.

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