Using 20x4 LCD display

Hello,

I would like to use a 20x4 LCD display attached to a Raspberry Pi
running FreeBSd 12.2.

I can talk to the display through the I2C interface, when I send
something the back light will turn off and on, so the link is
established.

What I cannot find is the sequence of codes to send in order to write a
character on te screen, to move the cursor around, etc.

All documentation I could find so far relate to Raspbian or Arduino and
are always using high level libraries (I could not find such on FreeBSD,
equivalent to WiringPi).

Whatever random characters I send to the screen, it persistently shows
alternating empty lines and lines or black boxes.

Any help pointing me in the right direction will be greatly appreciated.

TIA,

Olivier
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