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RSSI value in floating point

Bluez-devel Khairulmizam Samsudin 4 participants 7 messages Jun 21, 2008 – Jun 23, 2008 Bluetooth drivers

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Khairulmizam Samsudin

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#0 lore raw

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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maintainer
#1 lore raw

Hi,

Quoted 3 lines

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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#3 lore raw
Quoted 3 lines · Khairulmizam Samsudin

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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maintainer
#4 lore raw

Hi Andrew,

Quoted 5 lines
Quoted 3 lines

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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#5 lore raw
Quoted 2 lines · Marcel Holtmann

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.

Quoted 2 lines

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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#6 lore raw
In reply to Khairulmizam Samsudin

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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