Talk:RPi Serial Connection

From eLinux.org
Revision as of 07:18, 22 February 2012 by Spotthemaniac (talk | contribs) (confirmation of usb serial adapter usage)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search

I have confirmed that this adapter works with a synology TTL serial comm port. [[1]] also confirmed the voltage is 3.3 from this convertor as loads of people were worried about degradation or failure using a 5v ttl serial convertor Waiting on the real thing to try it out.

You cannot post new threads to this discussion page because it has been protected from new threads, or you do not currently have permission to edit.

USB serial connection to Raspian with systemd

The page was a little vague on how to do this with my version of Raspian. My uname -a:

Linux raspberrypi 4.9.41-v7+ #1023 SMP Tue Aug 8 16:00:15 BST 2017 armv7l GNU/Linux

My system uses systemd. This is what ended up working for me:

  1. I plugged a USB to female crossover serial cable into the Raspberry Pi
  2. With my Arch Linux PC, I plugged in a USB to male serial straight-through and plugged that into the female of the Pi's crossover
  3. Verify the /dev/ttyUSB* port (it was /dev/ttyUSB0 for me) on the RPi. Then execute a serial getty in Raspian: systemctl start serial-getty@ttyUSB0.service (if you want it to start at boot, do systemctl enable serial-getty@ttyUSB0.service)
  4. From my Arch Linux PC I was able to connect with minicom -D /dev/ttyUSB1

It shouldn't really matter which host gets the straight through or which gets the crossover. However, if the PC has a serial port connected to its motherboard, you can plug the female end of the crossover directly into the PC's serial port and won't need another cable.

Just wanted to share in case this is helpful to someone else. I plan to use the built in serial port to control another device, but even if you don't this is a handy out of band connection to a RPi and/or lets you interact with your RPi's TTY console without a monitor and keyboard.

15:31, 28 November 2017

Create a new page re: the manual configuration needed to prevent Linux from using the serial port

I suggest to create a new page regarding the manual configuration needed to prevent Linux from using the serial port and place a link here because a) the text of that section is by far much longer than the other 2 methods b) almost everybody will use the other 2 methods and very-very few the manual one

00:48, 20 May 2016

Glitch when serial port is opened

When the serial port is opened there is a 32 us negative pulse on TXD (http://www.raspberrypi.org/forums/viewtopic.php?f=44&t=49867). Although many devices are error tolerant and thus not affected by this glitch, some are not and cannot easily be modified to deal with it. I would like to add a section to this page describing the glitch and how it can be avoided. It is difficult to search for information about this glitch. I did not find the linked forum post until I included 32us in the search string, and I only thought to measure the pulse because I was writing a new forum post myself. The glitch occurs when the serial port is opened, so the solution is to keep it open. This can be accomplished in bash with:

cat >/dev/ttyAMA0 &

If there are no objections I will add a small section on this glitch to this page in a few days.

16:06, 25 July 2014