View unanswered posts | View active topics It is currently Sat Apr 27, 2024 6:37 pm



Reply to topic  [ 5 posts ] 
 EXPLODING MAX 232's 
Author Message

Joined: Mon Oct 07, 2019 2:41 am
Posts: 593
Max 232's have been around as the quick and dirty fix for RS232 lines with only a +5 volt supply.
With the last batch of MAX 232's or similar, they have been all crapping out. The only one working
is junk box MAX 3232 that I had kicking around. Are there any other ways to get +-12 from +5 volts
so I can use real RS232 chips, with low noise on the power supply?


Fri Feb 09, 2024 5:40 am
Profile

Joined: Sun Mar 27, 2022 12:11 am
Posts: 40
Where are you getting them from? If it's from china you probably got something else.

Also what are you using RS232 for?


Fri Feb 09, 2024 6:24 am
Profile

Joined: Mon Oct 07, 2019 2:41 am
Posts: 593
DockLazy wrote:
Where are you getting them from? If it's from china you probably got something else.

Also what are you using RS232 for?


I got them off Amazon so I suspect China. It was one of them cases I needed it yesterday.
Digikey is fast shipping, but they don't carry TTL any more. In most cases I order from China
for all my parts off ebay, as shipping from Hong-Kong or Poland is cheap and know in general
what I need, like bypass caps and sockets and resistors.

For now I got a single rs232 port, connected to the PC acting as terminal and a paper
tape bootstrap loader.
(I need to get a REAL TTY :) )
Later I want add a serial printer, and a second port for downloading files to disk, in my case compact
flash.

For PCB boards, I use PCBWAY from China. It takes about a week to have the PCB made and shipped to
me. They have good service and DHL is about $25 (US) shipping plus $25 import tax to Canada.

It is Kicad that I hate, because of all the stupid metric footprints, or not having footprints for things like switches.
I miss the Austrailan PCB programs like Autotrax, that were simple to use and easy mechanical routing like
memory address lines to the cpu.

If the second ram card works, then I need to revise the mother board PCB using better swiches and 2 oz
copper. About 2.5 amps I suspect on the +5 volt line.


Fri Feb 09, 2024 2:09 pm
Profile

Joined: Sun Mar 27, 2022 12:11 am
Posts: 40
Yeah Digikey is a bit of a mess.

Mouser still has plenty available. I assume you mean LS as the 74xx series chips are pretty much all no longer in production.


Sat Feb 10, 2024 8:52 am
Profile

Joined: Sun Oct 14, 2018 5:05 pm
Posts: 62
You could - at least to start with - use TTL Serial and one of the many TTL/USB serial adapters to get data to your PC.

This won't address the printer issue, but it would be a start.

And if the MAX devices continue to be a PITA then to address the printer issue, you could connect the printer serial port again with another TTL/USB adapter to your PC then there are USB/Serial adapters that will provide the correct +/- ~12v signals to a real RS232 device. I have used the Startech ones in the past with good results and they provide proper 9 and 25 pin models.

The issue then is how to plumb 2 USBs together on your PC - which is easy if you run Linux, there is a program called socat which lets you plumb things together. I used it myself a while back when I wanted to get my retro 65816 system taking to a real terminal - ttl serial to usb to my PC then a Startech usb -> 'real' RS232 to the terminal. It worked a treat.

-Gordon


Sat Feb 10, 2024 5:42 pm
Profile
Display posts from previous:  Sort by  
Reply to topic   [ 5 posts ] 

Who is online

Users browsing this forum: No registered users and 26 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group
Designed by ST Software