tag:blogger.com,1999:blog-1858053868211584958.post6099460963909044499..comments2023-06-03T16:34:34.767+01:00Comments on Bogology: Fake MAX3232 RS232 line drivers ?Eamonn McGoniglehttp://www.blogger.com/profile/15507058620638190745noreply@blogger.comBlogger13125tag:blogger.com,1999:blog-1858053868211584958.post-85163236477336935592021-12-27T11:03:24.162+00:002021-12-27T11:03:24.162+00:00Thanks a lot for the article! I face the same issu...Thanks a lot for the article! I face the same issue...<br />Now I need to find a solution...<br />I wanted to buy this version with a different architecture (with dismountable chip) so then replace the chip by the official one. The module is available here:<br /><br />https://fr.aliexpress.com/item/33044933594.html?spm=a2g0o.cart.0.0.26993c00zS0c3D&mp=1<br /><br />But still a problem : Where can I get the official chip with the same case ? It seems to be out of stock on TI website.<br /><br />Or is it possible that even if it's still a copy, this kind of chip will work better than the SMD version?<br /><br />Anyone has a simpler solution to propose me?<br /><br />Thank you.Anonymoushttps://www.blogger.com/profile/00761373085762690962noreply@blogger.comtag:blogger.com,1999:blog-1858053868211584958.post-85350255651643436872019-10-29T06:08:24.154+00:002019-10-29T06:08:24.154+00:00I'm using Chinese MAX3232 boards without DB9. ...I'm using Chinese MAX3232 boards without DB9. When connected to raspberry pi's 3.3 volts the charge pump circuit doesn't pump anything (No +- 6v). With a different supply, it works most of the time.Bryan Jensenhttps://www.blogger.com/profile/06372436715344195188noreply@blogger.comtag:blogger.com,1999:blog-1858053868211584958.post-78941943123875285822019-06-04T20:44:33.443+01:002019-06-04T20:44:33.443+01:00I too just fell into this trap ... had a batch of ...I too just fell into this trap ... had a batch of MAX3232 chips from China for a custom board ... worked fine with an earlier prototype (and MAX232), but with the new chips it also showed the echo ... same behavior ...<br />Will try the trick with the Zener and see if that helps ... anyway, on the chips I have, even a moderate voltage of +-7V causes the echo (which comes out at about +6 to -2V, weirdly)Garryhttps://www.blogger.com/profile/08993001217485254765noreply@blogger.comtag:blogger.com,1999:blog-1858053868211584958.post-45213751973186879602018-02-06T03:19:29.686+00:002018-02-06T03:19:29.686+00:00Hah! Right you are sir! I got no satisfaction with...Hah! Right you are sir! I got no satisfaction with the voltage divider (was too impatient to wait for a response). I tried large resistors and small resistors. Unlike Goldilocks, I could not find the right one. The funny thing is that the voltages are +/- 9.6 or so volts-not terrible high. I checked the rs232 adapter with a loopback and by connecting them back to back. Everything works until the voltages become "high (9V)". Now where to find legit MAXIM adapters... GregShttps://www.blogger.com/profile/09124876146007663073noreply@blogger.comtag:blogger.com,1999:blog-1858053868211584958.post-74703442290852765822018-02-05T18:16:19.749+00:002018-02-05T18:16:19.749+00:00Ok. I'm looking to use these for a prototype e...Ok. I'm looking to use these for a prototype electric vehicle, so I'd rather not risk it going crazy after a few minutes. Not with an actual driver on board in any case.Anonymoushttps://www.blogger.com/profile/12106211701676107263noreply@blogger.comtag:blogger.com,1999:blog-1858053868211584958.post-81554878811416119962018-02-05T12:53:26.269+00:002018-02-05T12:53:26.269+00:00I wouldn't absolutely count on a resistor divi...I wouldn't absolutely count on a resistor divider doing the trick. The problem is that you have no certainty about the "stiffness" (output impedance) of the source nor the input impedance of the destination. This means that the usual resistor-divider calculation (which assumes a low output impedance and a high input input impedance) won't necessarily produce the result you want. You would need to find a balance between making the resistor values high enough that they won't load down the output too much yet low enough that they can supply adequate current to the destination. It might be a fine balance. The diodes have the advantage of not being affected by either of those things.Eamonn McGoniglehttps://www.blogger.com/profile/15507058620638190745noreply@blogger.comtag:blogger.com,1999:blog-1858053868211584958.post-63273433793680629302018-02-03T15:00:15.219+00:002018-02-03T15:00:15.219+00:00Hi, Do you think that putting a voltage divider wo...Hi, Do you think that putting a voltage divider would work as well as the zener diodes you are using? Thank you. I have been pulling my hair out to find why I get no RS232 comms...GregShttps://www.blogger.com/profile/09124876146007663073noreply@blogger.comtag:blogger.com,1999:blog-1858053868211584958.post-135487087118041572017-12-16T22:03:29.737+00:002017-12-16T22:03:29.737+00:00WOW. Just WOW. I spent hours diagnosing this issue...WOW. Just WOW. I spent hours diagnosing this issue, thought it was my wiring bad. I will order genuine MAX3232 to replace and see if it works. Thanks a lot man!Unknownhttps://www.blogger.com/profile/12212974069183538866noreply@blogger.comtag:blogger.com,1999:blog-1858053868211584958.post-60055413694914891492017-11-27T18:44:45.269+00:002017-11-27T18:44:45.269+00:00I think the MAX3232 is more complex than an FTDI. ...I think the MAX3232 is more complex than an FTDI. You can build an FTDI with a microcontroller and firmware, you cannot do the same with the MAX3232.Totoxahttps://www.blogger.com/profile/10549386493300346508noreply@blogger.comtag:blogger.com,1999:blog-1858053868211584958.post-90416033934450109692016-03-12T18:55:02.720+00:002016-03-12T18:55:02.720+00:00Thanks for sharing! I was trying everything I coul...Thanks for sharing! I was trying everything I could to eliminate and diagnose cross talk,, and I never suspected the chip itself to be fake. Just changing it to a genuine unit, even the regular 5V version, helped!piopawluhttps://www.blogger.com/profile/14322597254624304702noreply@blogger.comtag:blogger.com,1999:blog-1858053868211584958.post-7028897949227680122015-11-06T14:02:07.988+00:002015-11-06T14:02:07.988+00:00Hi Eamon,
I had the sam issue with a different ch...Hi Eamon,<br /><br />I had the sam issue with a different chinese MAX3232 board.<br />Around five minutes after power up, every character sent to board was echoed and it was corrupted.<br />First I thougth that the chip has been destroyed by ESD and I used a new board (I bought 4). It worked, but only for five to ten minutes too. <br />So I ordered genuine MAX3232's and soldered them onto the board. They work without any problems. When looking to the genuine MAXIM chip yould will notice that it looks much better. The laser etching is deeper and the modling is much sharper. But when I was looking to fake chip for the first time, it seemed to be fine.<br /><br />It's funny, that the chinese industry is able to make working FTDI clones but unable to make a simple MAX3232.<br /><br />Paul<br />Ransepanshttps://www.blogger.com/profile/15387789260453871645noreply@blogger.comtag:blogger.com,1999:blog-1858053868211584958.post-67014583459234864702015-04-27T07:12:18.809+01:002015-04-27T07:12:18.809+01:00i also seem to have this issue, actually i use a u...i also seem to have this issue, actually i use a usb to ttl adapter to connect to PC, then ttl to rs232 and then a null modem cable to conenct to a box running pfsense, the issue happens when i boot pfsense, during boot it waits for some commands for 5 seconds to goto shell, during that period nothing should goto pfsense but it seems the crosstalk makes it auto type some characters.<br /><br />for me the issue is when i have the adapter conenct to PC and then i reboot pfsense with PC powered on then it will reboot but if PC is off with no power so no power on usb to ttl as well as this adapter then there is crosstalk and pfsense wont boot unless i remove the serial cable. So its like there is crosstalk when there is no power in the max3232 chip.Bipinhttps://www.blogger.com/profile/12035218539174576985noreply@blogger.comtag:blogger.com,1999:blog-1858053868211584958.post-53615135000461608982015-04-27T07:12:03.575+01:002015-04-27T07:12:03.575+01:00what i suspect is the newer adapter have extra cap...what i suspect is the newer adapter have extra caps and some resistors which r required to overcome this crosstalk thats y this 4 cap circuits dont work properly as they lack few extra coponentsBipinhttps://www.blogger.com/profile/12035218539174576985noreply@blogger.com