Arduino as a Modbus Master ( RTU485)

Hello!

What would be the best library for using Arduino as Modbus master? Also I would be very pleased for an example how to write a register with arduino. Example register how to set register 4561 to an value 0 or 1?

Br, Uikru

"the best" depends on what you are looking for.

for repeating retrival only I prefer the simple modbus from Juan Bester: https://github.com/jecrespo/simple-modbus or https://drive.google.com/folderview?id=0B0B286tJkafVSENVcU1RQVBfSzg&usp=drive_web

for one time setting of values others might be more suitable.