Enabling uarts, i2c and spi

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1

Hello all.

First off, I’d like to thank the community for their continuing help!

I’m trying to get understanding on many things at once here, so I’m going to fire off a series of questions. Please bear with me here :slight_smile:

  1. What is the best way of enabling uart1, 4 and 5, i2c1 and 2 and spi1? I understand I have to modify dtb files. Any tutorials on doing that on ubuntu?
  2. Where is uart3_rxd?
  3. I’d like to connect the gps to uart5, but those pins are used by the boot config. What are the consideration there?
  4. If I do ls /dev there are a bunch of tty devices, how do I know which one is what? I’m googling how to enable uarts on bbb and I’m seeing the references to tty0xx. No such thing in /dev, even for the uart0 that is enabled.
  5. Also, if I’m connected to bbb via serial on j1 and I also telnet to it and do echo “hi” > tty, shouldn’t I see “hi” on the serial terminal?

I’m using ubuntu-13.04-minimal-armhf-2013-08-25 and Robert C Nelson’s 3.12.3-bone9 kernel.

Thanks and best regards,

Miro

2

To answer my own questions 1, 4 and 5 here’s the link that makes this very clear:

http://learn.adafruit.com/introduction-to-the-beaglebone-black-device-tree/exporting-and-unexporting-an-overlay

This is easier than I thought. I’m loving it!

That leaves 2 and 3:

  1. Where is uart3_rxd?
  2. I’d like to connect the gps to uart5, but those pins are used by the boot config. What are the consideration there?

Thanks,

Miro

3

if you are using 3.12 the uart is broken https://github.com/RobertCNelson/linux-dev/issues/16

4

Haha, well, darn, just as I thought I caught the break… What does it mean to “manually patch the dtb file and add ttyO1”?

Miro

5

I think doing a new device tree for ttyO1

6

There is no UART3 RX, I believe the pin wasn’t exposed for some reason. UART5 works fine (and I too have a GPS wired to it and working nicely) under kernel 3.8. Although you have to disable the HDMI, see http://www.logicsupply.com/blog/2013/07/18/disabling-the-beaglebone-black-hdmi-cape/. You can’t yet do this under 3.12 last time I checked.

7

Thank you all!

Miro