RS 232..need help..

[cwt]

Hi..I am currently doing a LED dot matrix display project. My aim is to display characters from a textfile to the external dot matrix display. I'm going to use RS 232 to interface with my circuit. So i have a few doubts. Hope you can help me answer my doubts. Thank You!

Can anyone tell me where to get more details about RS 232 serial port??
(Eg. how to interface with it?,which one is better?25pins or 9pins?, data sheet)

Is RS 232 buffer used as a voltage converter to convert voltage output from computer to a higher serial voltage level? Or it is used to convert voltage level from external devices to TTL voltage level?It can be used for both operation?

Is it a must a RS 232 serial port must used with RS 232 buffer?

 

[Nigel Goodwin]

Hi..I am currently doing a LED dot matrix display project. My aim is to display characters from a textfile to the external dot matrix display. I'm going to use RS 232 to interface with my circuit. So i have a few doubts. Hope you can help me answer my doubts. Thank You!

Can anyone tell me where to get more details about RS 232 serial port??
(Eg. how to interface with it?,which one is better?25pins or 9pins?, data sheet)

It makes no difference, the only difference is the size of the plug - basically older equipment used 25 pin plugs, and later ones use 9 pin.

Is RS 232 buffer used as a voltage converter to convert voltage output from computer to a higher serial voltage level? Or it is used to convert voltage level from external devices to TTL voltage level?It can be used for both operation?

It works both ways, have a look at my PIC RS232 tutorial.

Is it a must a RS 232 serial port must used with RS 232 buffer?

No, there are many ways of doing it without a 'buffer' - even a single resistor can be used, which I suppose is a 'buffer' in a way?.

 

[gerty]

Take a look at this site I think it explains what you're looking for:
https://www.camiresearch.com/Data_Com_Basics/RS232_standard.html#anchor242192

 

[cwt]

Nigel, the electronic god, thanks for your help. :lol:
How to be an electronic god?!!

Thanks gerty for the website you recommend. I gain extra information from there.

What is MAX232 for??(boost up TTL signal and step down RS232 signal?)
Does MAX232 invert the voltage signal?

 

[Nigel Goodwin]

What is MAX232 for??(boost up TTL signal and step down RS232 signal?)
Does MAX232 invert the voltage signal?

Yes to all, IC's are generally designed to work with a MAX232, so the inversion is accounted for - for example, the hardware UART's in PIC's connect directly to the MAX232 - they are designed to do so. This means you can't use the hardware UART unless you provide a hardware inverter, but you can still do it easily in software.