Serial connectivity


9 posts
by sgtboost » Tue Jun 05, 2012 4:32 pm
Hi,
I've been combing the forums but I haven't found a decent guide for what I'm after. I'd like to incorporate a serial interface into the RPi - just like you'd find in a PC laptop. My goal is to use that serial port on the RPi to connect to different switches, routers, etc.

Anyone have a decent how-to setup the GPIO to be used as a serial port?
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by jbeale » Tue Jun 05, 2012 5:55 pm
All you need is a level converter circuit to change the 3.3V logic level up to the +/-12V RS-232 standard levels, and the serial port connector itself. Here is one description of how to do it with a Maxim MAX3232 chip: Adding a serial console to the Raspberry Pi

You can buy such a module prebuilt from Ebay for example:
http://www.ebay.com/itm/RS232-Serial-Po ... 0438518755

there are cheaper ones, but be sure to get a chip that will accept and provide 3.3V logic levels to the R-Pi, which does NOT have 5V tolerant I/O pins. I believe the cheaper MAX232 based modules use 5V logic level, instead of 3.3V.
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by tech_monkey » Tue Jun 05, 2012 6:07 pm
I posted a similar question a while ago. on this forum. viewtopic.php?f=63&t=5219,
and there is also this one as well viewtopic.php?f=9&t=2565
http://www.casatech.eu
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by royger » Thu Jun 14, 2012 10:26 am
I have no RS232 on my laptop, from what I read I think something like this might work:

http://www.amazon.com/Micro-SATA-Cables ... y_e_text_b

It says it supports TTL 3.3V, but it uses a different chip, can someone verify it will work?

Thanks!
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by DMcK » Sun Jul 01, 2012 5:05 am
I'm going to use raspmc on my Pi and need a serial port to send serial commands to my TV.

So I just ordered this one for only $3 including shipping and jumpers. It could take about a month to get to me as it's coming from China, but that is about 2 months faster than it will take to get my Pi! :-(
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by jbeale » Mon Jul 02, 2012 12:54 am
Are there any laptops now made that still have the original RS-232 level serial ports? Most I've seen have only USB ports. For about $2.50 you can get a USB->logic-level serial module that connects a laptop or PC USB port to the UART on the RPi's GPIO pins, and in fact you can also power the R-Pi directly from it as well- if you don't have anything else connected at least- as shown in this photo.

https://plus.google.com/photos/10992823 ... banner=pwa

Search for 'PL2303HX module' on ebay to find one, that comes with 4 jumper wires also.
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by TonyD » Mon Jul 02, 2012 12:44 pm
If any one is interested here's a board design I did for a 3.3V RS232 board. MiniPiio RS232

It uses a 3.3V MAX3232 and connects directly to the RPi Expansion Header

Image
Tony
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by el_toro » Wed Jul 04, 2012 1:09 pm
[quote="jbeale"]Are there any laptops now made that still have the original RS-232 level serial ports? Most I've seen have only USB ports.

Fujitsu Lifebook E-Series

All us old Unix dinosaurs were shelling out for USB-Serial dongles which we still need for COM-A on many systems.
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by TonyD » Wed Jul 04, 2012 4:24 pm
None that I've seen recently. I thought the Panasonic ToughBooks might, but couldn't see any with a RS232. We tend to buy old Dells off ebay, but a decent spec'd one with RS232 can be sold for a lot more than you expect.
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