Quote:
Originally Posted by Frenko
Thanks!
So if I measure the tension at 1.8v on the serial side of the cable I should be ok?
I'm particularly interested in knowing if it's an opinion or a fact!  
And, I don't know if it's a stupid question, but what about tx/rx? Can a transistor cause data losses or any other problem?
Thank you guys 
f  |
I would have to have your unit in front of me so I could read the resistances of your circuit. If I knew the circuit resistance then given the source voltage. 3.3 v and then make a good guess of the current needed
Then using ohms law the value of the dropping resistor could be calculated to be used to give your power supply a output voltage of 1.8v .
If you know anyone that is good with electronics, or amateur radio (ham) operator that knows their stuff. They could help you figure it out.
Just knowing your source 3.3v and desired output voltage 1.8v is not enough for me to tell you what value dropping resistor needed. I would have to have a good ideal of the current/resistance of the circuit before that can be calculated accuracy, but I figure something between 60 and 80 ohms , but that is only a best guess. You could try these values and see if the supply voltage drops across them to give you the 1.8v you want.
Imo is just that , my opinion or best guess.
Hope this helps!
Charles
Edit: On the data lines I do not think anything needs to be done, if the supply voltage is correct. The data pulses (Square wave, assuming digital) along the lines tx/rx should be controlled in the unit its self and their voltages are of no concern. The only concern is the supply voltage feeding the circuit.