Photon vs Core - RSSI Readings?

So I am using the RSSI function on the Photon to read the WiFi Signal Strength.

The reference docs say the following but I think this may be different on the Photon vs the Core.

When I have my phone which is my Wifi hot spot right next to the Photon or very close I get DB readings of up to 11.

I was trying to use the Map function to get the -127 to -1 Db readings down to a 0-100% signal strength but I kept getting numbers over 100% when my phone was right next to the Photon.

So I looked at the raw output of the RSSI function and the highest number I could get was 11. The docs say it should be -1 max. Is that for the Core only?

I don’t know for sure on Photon but for the Core, positive values indicate an error and +11 would mean that the WiFi chip driver got confused.

I searched a bit for the RSSI range for WICED but did not find anything very useful. There was comment in a file on github saying they fixed a bug in RSSI:

  • The wiced_scan_result_t structure now includes a flag to indicate reception of an off-channel scan result
    (rather than returning the RSSI of the result as +200dBm)

I don’t think that +11 dB would be a meaningful RSSI for normal access points and phones but it could be a relative measurement with a funny 0 dB value. I think the reported readings can only really be interpreted on a relative scale, comparing one reading against the next–they are not calibrated in any way that I know of.

@BKO I suspect that most people are not paying attentin to the RSSI readings and even fewer are getting close enough to the WiFi source to even see the db rating go over -1 which should be the max.

Also I have the external antenna attached and I have the external antenna code running also. So maybe the chip antenna would never get that high, have not checked that way yet but I suspect the same issue.

So for most people this would never even come up but I’m for sure seeing readings above -1 in the range of 0-11.

If anybody else can confirm this it would be helpful.

I’m getting this now too, if I put my Photon which is using a u.FL external antenna next to my router, my reads go into the positive range, but seemly skipping over 1 and 2.

@KeithM I’m glad I’m not the only one experiencing this.

My solution was to scale the reading from -128 to +11 but that still does not provide an answer to why this is happening when the docs say it should not go above -1. Something is not right. .

1 Like