• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Controlling a digital potentiometer through the seriallport

Status
Not open for further replies.

iver89

New Member
Hi! I want to controll a digital pontetiometer from my seriallport. The potentiometer is DS1804 from Maxim (datasheet). How do I make a signal go high or low, and what do it actually mean? I'm not a superprogrammer, but I know some Pascal.

Anyone?
 

kinjalgp

Active Member
You cannot connect serial port directly to your potentiometer. Thats because serial port operates at +-12V which will blow up your potentiometer. You first need to convert this RS232 signals to TTL using level shifter ICs like MAX232.

Also you can't send data to potentiometer using its TXD pin because the speed of transmission is fixed for this pin depending on baud rate and you have no control over individual bits to be sent. Instead you can use other signals like RTS and make it high/low (1 and 0) with required speed.
 

Exo

Active Member
Well, it depends.

A high means a logic '1' ; and low means logic '0'.
However how this is implemented in hardware depends on how the designers choose to do it...

TTL signals for example (the ones you need to control the digital pot, and the same signals the pc parallel port uses) use a 0V to indicate low; and 5V to indicate high.

RS232 signals (the serial pc port) use approx. +12V to indicate a high and -12V to indicate low.
 

Exo

Active Member
I think you better use the parallel port. The parallel port allows you to manually set a certain output high or low in software, wich is what you need to drive the digital pot.
A serial port however was only designed to send data between PC's or modems. The data sent by a serial port is 'encoded' in a specific way, and you need an UART to decode it; if you use the parallel port you can probabely hook it to the digital pot directly.
 

kinjalgp

Active Member
Exo said:
A serial port however was only designed to send data between PC's or modems. The data sent by a serial port is 'encoded' in a specific way, and you need an UART to decode it
Not necessarily. If you are using RXD and TXD pins then only you require UARTs to decode data. While you can use rest other control signals as individual digital output pins and you can pull it low or high using software. One such pin is RTS.
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top