Hello @DanK
actually there is an AMS1117 version with exactly the output voltage you measured: 2.85 V - coincidence?
From the AMS1117 datasheet - feature list: Three Terminal Adjustable or Fixed Voltages* 1.5V, 1.8V, 2.5V, 2.85V, 3.3V and 5.0V
But yes, the input voltage is probably on the low side.
Thanks
Felix