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PPP and Red Pitaya

Posted: Mon Mar 05, 2018 9:28 pm
by queissman
I need to conect to the RP via a radio transmitter which has an UART interface and use ssh. So basically I need to communicate with the RP using ssh via the UART port. To that end there is the ppp protocol. A ppp daemon is running on the RP and the host side. Once they have done their handshake one can use ssh, scp ping etc.. This is how it should be.

Now, ppp on the host PC (Ubuntu) works, the ppp deamon is running, no problem. But, I cannot get it to work on the RP side, as upon starting the ppp daemon on the RP it "cannot find the /dev/ppp" node, even though I created it and set permissions to 600. The second error message is "please load ppp_generic kernel module". To solve this I already put "alias char-major-108 ppp_generic" into the /etc/modprobe.d/modules.conf. I also created a /etc/modules.conf just in case it is looking there for the module.

Has anyone have had this issue and solved it? Thanks!

Re: PPP and Red Pitaya

Posted: Mon Mar 05, 2018 10:02 pm
by pavel
If you're using the SD card image from

http://redpitaya.readthedocs.io/en/late ... Dcard.html

then the Linux kernel on this SD card image doesn't have the PPP drivers enabled.

I can think of at least two solutions:
  • enable the required drivers, rebuild Linux kernel and copy it to your SD card
  • try the SD card image based on Alpine Linux with the PPP drivers already enabled
The SD card image based on Alpine Linux can be downloaded from

http://pavel-demin.github.io/red-pitaya-notes/alpine

The Alpine Linux documentation can be found at

https://wiki.alpinelinux.org/wiki/Using_serial_modem

Re: PPP and Red Pitaya

Posted: Mon Mar 05, 2018 10:15 pm
by pavel
Looks like the Alpine Linux instructions aren't very up-to-date.

I think that

Code: Select all

modprobe ppp
should be replaced with

Code: Select all

modprobe ppp_async
.