HITL with voxl 2

Tamas Pal 0

tamas@tamas:~$ echo 1 | sudo tee /sys/bus/usb-serial/devices/ttyUSB0/latency_timer
tee: /sys/bus/usb-serial/devices/ttyUSB0/latency_timer: Permission denied
1
tamas@tamas:~$ ls /sys/bus/usb-serial/devices/ttyUSB0/latency_timer
ls: cannot access '/sys/bus/usb-serial/devices/ttyUSB0/latency_timer': No such file or directory

How to fix it ?

Eric Katzfey

@Tamas-Pal-0 What do you get with ls /dev/ttyUSB*?

Tamas Pal 0

@Eric-Katzfey
I got this

tamas@tamas:~$ ls /dev/ttyUSB*
/dev/ttyUSB0

I am unable to modify anything inside /sys/bus/usb-serial/devices/ttyUSB0 with root user also. How to fix it?

Eric Katzfey

@Tamas-Pal-0 I'm not sure. This works in our development environment so something must be different in your environment. What version of Linux are you using? What cable are you using?

Tamas Pal 0

@Eric-Katzfey
The issue is fixed. It was a hardware issue. I changed the ftdi cable and the issue was solved. The previous FTDI cable was not allowing me to change anything in /sys/bus/usb-serial/devices/ttyUSB0 directory. The file latency_timer was also not there. However with the other cable, there is no such issue. Thank you for your valuable input.

Tamas Pal 0

For 3.3v J18 jst port which port of ftdi cable should be used, CTS# or RTS# ?

Eric Katzfey

@Tamas-Pal-0 For UART it is just GND, TX, and RX

Tamas Pal 0

@Eric-Katzfey you mean we only have to connect 3 pins in j18 port ?

Eric Katzfey

@Tamas-Pal-0 Yes, the fourth pin is power and we don't want that one.

Tamas Pal 0

Is there any way to verify that FTDI cable is connected properly with J18 port ?

Eric Katzfey

@Tamas-Pal-0 The easiest way would be to recompile the modalai_dsp PX4 driver to add more debug messages. But if you aren't comfortable with that then we'll need to come up with something else.

Tamas Pal 0

How to do that? Is there any other way to this ?

Eric Katzfey

@Tamas-Pal-0 The simulator will be sending heartbeat messages out over the serial cable. You can use the screen program to see if anything is coming from voxl 2 in the serial cable.

Tamas Pal 0

@Eric-Katzfey How to use screen program in this case ?

Eric Katzfey

@Tamas-Pal-0 screen is just a standard Linux program. There are many ways to check the output of the serial port. To start, you could always just do cat /dev/ttyUSB0 and see if anything is coming out. This post shows how to get a hex dump: https://superuser.com/questions/1402386/view-serial-device-output-in-console-in-hex

Tamas Pal 0

The problem is solved. The problem was with ftdi cable. Thank you for your valuable inputs

Eric Katzfey

@Tamas-Pal-0 Excellent! How were you able to determine that it was the cable?

Taylor Presley

@Eric-Katzfey @Tamas-Pal-0 For future users troubleshooting HITL setup, I was having the same issue as above. This cable would not allow me to set the latency or share data with the VOXL 2 through J18 port, but this cable works as intended.

Tamas Pal 0

@Taylor-Presley Right. Some cables work some don't.