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How To Build Your Own RS232 To TTL Converter

By on September 26, 2017
rs232 to ttl converter diagram









Hi good peoples!

Couple of days ago I got a request to update some sort of firmware on a not so typical microprocessor, the LPC2119 type.

As I read many pages on the internet I saw there is a sort of adapter so called “USB to TTL adapter” who can communicate through with the uC. I had not the time to order one but I give a try to make one for the COM port. Actually it is an RS232 to TTL converter which I found better from my opinion than that USB to TTL adapter.

Here is why I like more this RS232 to TTL adapter than the other one:

– can be used on a real RS232 port.

– it is a stable voltage level converter

– can be used on USB port too ( through USB to RS232 converter )

– there is no VCC ( somebody would say it’s a disadvantage but wait…) *

– it is a real hardware stuff, no emulation etc. ( if it is used through a real com port )

– can be built really cheap and easy

Disadvantages of this device:

– it’s old school

– has to use an external power source ( which is actually not bad! )

For what to use such a device?

If you repair electronic where are cpu’s need to be updated the firmware, or you just practicing on some development board where are used some sort of cpu for communicating with the computer, or you maybe can also use it to debugging some sort of data from a desired circuit etc…

Enough talking but go to building one. Here is the schematic what I done and the whole part list to build this simple but usable device.

Part list:

– MAX232 ( whatever manufacturer )

– Capacitor of 2.2uF

– Some wiring for connection or make a small pcb

– External power source

* Personally I don’t trust device which use the power from the USB port.

Lot of time I run into trouble, killed eeprom content’s, killed the uC’s firmware’s etc. because a voltage drops on the USB port. The USB port can’t manage more current than 500mA (I talk about the USB 2.0), which is not a small amount but also not enough if on the same USB controller are attached a mouse, scanner etc.

You can run out of power and the USB controller will shut down until you read or write the content to or from the desired device.

Here is the schematic:

rs232 to ttl converter schematic diagrams

I know, this is not a big deal but it was very handy for me at the moment when I needed. You can mod this as you wish for your meaning, it is a nice tool when it comes to the moment to finish a job, but you don’t have the right tool and you also can’t wait for delivery.

Here is a picture about a commercial version, just for idea how you could also build one.

rs232 to ttl converter

I hope you enjoy this tutorial and will save lot of repair time.

This article was prepared for you by Christian Robert Adzic from Novi Knezevac-Serbia.

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  1. Albert

    September 26, 2017 at 1:54 pm

    Very nice DIY instruction guide on how to make such a rs232-ttl converter Chris! Many readers are just waiting for these Make-it-Yourself articles. Recently I needed such an interface to program my Gotek Floppy Emulator Drive to make it an "Cortex" Amiga Floppy Emulator. If you do want to build such an rs232 adapter you still need to order a MAX 232 chip if you do not have one. Therefore I prefer this very cheap and useful adapter that also just uses the USB port without the need of an external 5V connection which simply worked great!
    And this complete interface that only costs about one dollar/euro is probably a better alternative instead of ordering a single rs232 MAX 232 chip which probably costs the same!

  2. Parasuraman S

    September 26, 2017 at 2:11 pm

    Excellent! Something new that I could get to bite to learn!

  3. Yogesh Panchal

    September 26, 2017 at 2:16 pm

    Christian Robert thanks for information on Rs 232 converter

  4. Henrique Jorge Guimarães Ulbrich

    September 26, 2017 at 10:17 pm

    The efficiency resides on the simplicity. Handy, cheap and effective. Cheers, Christian.

  5. Robert Calk

    September 26, 2017 at 10:38 pm

    Good job, Chris. Thanks.

  6. Anwar

    September 27, 2017 at 10:19 am

    Good job chris and nice for diy' about i2c..can use it also?thanx

  7. Ulises aguilar pazzani

    September 29, 2017 at 11:53 am

    Great Chris thks for sharing

  8. allala

    October 2, 2017 at 4:11 pm

    grand merci-big thanks

  9. Humberto

    October 5, 2017 at 11:27 am

    Thanks for the information.

  10. Ruturaj Desai

    October 11, 2021 at 11:33 pm

    can you show for RS232 to RS485 converter ??


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