RS232 emulates I2C for 24cXX memory programming

Sometimes you need a quick and easy solution for programming serial EEPROM memory chips. I think the easiest and well-known method is to use a simple programmer adapter with very few components:

This adapter is connected to the RS232 port, and there is no need for an additional power supply as it comes from the PORT pin. The adapter is compatible with JDM Programmer so that you can use its programming software like IC-PROG. Just make a couple of settings, and you are ready to go:

Download IC-PROG for free.


  1. Is it correct that the Clock and Data lines are connected to the RTS (pin 7) and DTA (pin 4) pins of the RS232 cable?

    That seems odd. I’d think it would be connected to RTS and TXD pins.

  2. I guess this depends on IC-Prog settings.

  3. I’m guessing it pulls current from the TXD pin, given this pin goes into the voltage regulator.

    The other pins can easily be toggled in VBasic, and TXD can’t.

    That makes sense.

  4. can read but can’t write the 24cxx

  5. can read but can’t write the device,help

  6. I do not have 78L05(100ma 5volt regulator) but I have LM7805(1A 5volt regulator). Can I use that? also, 5K is not a standard resistance, can I use 4.7Kilo-ohm or I have to parallel two 10Kilo-ohm resistors. Email me qiuckly at arupbsk AT gmail DOT com . Thanks

  7. u can use LM7805 in any application where 78Lhas same function as the latter,only that it can take more current which is desirable when u have a large load to be drive.the problem is that it will sink more current from your source and your batteries can run down quickly

  8. What about the 5K resistors? Can I use 4.7K ones ?

  9. Yes, you can also use the 4.7k resistors!
    It also works with ponyprog – it fails at \probe\ button, but it works – tested with a 24c32.

  10. is it working with 25Cxx family or i have to use another schematics ,if so where can i get it ?

  11. can write, but take to loooooooong time, do you have another schem

  12. Hello, I am having some difficulties on a 24c04 eeprom because I can’t read or write. I just read 00FF.

    -I ticked the “Use MCRL as Vcc.

    -I am using the JDM programmer on COM2 (I tested Direct I/O and Windows API).

    -I enabled NT/2000/XP driver and I am running icprog in Windows XP SP3.

    -I tested all signals DataIn/DataOut, Clock, MCRL and Vcc. When I tick each test, the signal is running around 4.8V.


  13. Problem semi solved.

    I am using PonyProg with the above schematics using the following definitions:

    -I/O Port Setup -> Serial -> SI Prog API (COM Port.
    -None signal is inverted.
    -The rest definitions are default.

    I also tried WinPic800 without any luck.

    Any trouble just ask. =)

  14. My programer didn’t work

    On RS232 pins out voltages are:
    Pin1 0,15V ; Pin2 0,15V ; Pin3 -11,05V ; Pin4 -11,05V ; Pin5 GND ; Pin6 0,15V ; Pin7 -11,05V;
    Pin8 0,05V

    My motherboard is ASRock P4i4D+

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