FNB58 reboots

[PlainName]

Had a chance to try this now to my Nothing (which is allegedly 33W capable). I'm using a GMM 120W charger and typically get 24W as shown on a cheapo USB cable-with-display. Insert the FNB58 into the chain and after an initial restart when the phone is attached, it goes as expected: climbs to 24W and stays there.

Then I unplug the phone and the FNB58 show no current but 9V still. Plug the phone in and I get about 3W for a short while, then the FNB58 reboots and comes back up showing 5V, 10W. After a few seconds, the voltage drops to 4.7V and then the FNB58 reboots and repeats the 5V, 10W, reboot thing. Seemingly forever.

If I disconnect and reconnect the charge the same thing happens (the FNB58 sucks power from the phone in that case). The only way out is to disconnect everything and start again from scratch.

I tried connecting a second power source to the micro-B (PC) connector, and that prevented the initial reboot-on-connect, but on disconnecting and reconnecting the phone it went back into the 5V, 10W, reboot loop.

With the FNB58 out of circuit, no problem: phone always ends up at 24W.

Is this normal behaviour for the FNB58 or do I have a borked one?

[Edit: added video]

[electr_peter]

Is "PD COM" switch on FNB58 set to ON or OFF? It should be in OFF position for it to be transparent to USB negotiation. If it is ON, it can interfere.

[PlainName]

I don't have (or can't find) a PC COM switch. Settings-wise, it's factory defaults.

[Kean]

I don't have (or can't find) a PC COM switch. Settings-wise, it's factory defaults.

The "PD COM" switch is on the front edge to the right of the Type-C connectors.

[PlainName]

Duh! Yes, it was set to ON. Changed to OFF and appears to be OK now. 

Thanks very much. Don't know how I missed that - after electr_peter's post I checked all 6 sides of the thing and still missed it 

[Kean]

This is useful to know.  I only just got mine, and have only had a quick play so far.