# How to get RSSI of Bluetooth, specfically HC-05

We purchased a Bluetooth device EGBT-045MS in hope that we will be able to get its RSSI. Do you have any idea how to do this?

## 1 Answer

First you send an INQM command (Set inquiry access mode), e.g.

AT+INQM=1,9,48


1 specifies access mode RSSI, 9 specifies the max # of devices to be discovered, and 48 is a timeout value

Follow this by a INQ command (Query Nearby Discoverable Devices)

AT+INQ


It will respond with lines like:

+INQ:1234:56:0,1F1F,FFC0


(up to nine responses in this case, set by the INQM command). Last entry is followed by an OK.

The first parameter is the address of the discovered Bluetooth device; all digits are hexadecimal. As shown here, it is in what is called NAP:UAP:LAP format.

The middle parameter is a type field.

The last parameter in the returned string is the RSSI value. Different makers of Bluetooth modules encode the RSSI value in different ways. From what I can tell looking at other documents, this module always returns 16-bit negative numbers in the range FF80 (or maybe FFC0) to FFFF. So a higher number probably means a high signal strength.

• On my HC-05 the command must be AT+INQM=1,9,48 (add an equals sign) – Houen Apr 16 '14 at 8:45
• @Houen You are correct, I left off the = sign. I've updated my answer. Thanks. – tcrosley Apr 16 '14 at 11:32