Current Sensing with ACS712 on Beaglebone Black
Yes you can use a voltage divider. Formula for a voltage divider is:

Vout = Vin * (R2/(R1+R2))

Vin is the voltage that goes in the voltage divider, I assume that it will be 5 volt in your case. Choose a value for R2, like 1000 ohm

1.8V = 5V *(1000 / (R1 + 1000))

1000/(R1 + 1000) = 1.8V/5 = 0.36

2777,78 = R1 + 1000
R1 = 2777,78 - 1000 = 1777,78

A nice value for R1 would be 1,8k ohm. when Vin is 5v, Vout will be like 1.78V, maybe it's wise to choose 2k ohm or 2.2k ohm instead, just to be a bit more safe.