Posts made by Robert Jensen

The voltage drop across the LEDs will be less than 1 volt. Two in series should work fine. Just reduce the size of the current-limiting resistor, if necessary. As stated above, two in parallel demands more current, which could be a problem. In series, the current lighting one LED is the same current lighting the second LED. The Omega won't know the difference.

Thanks. Where did you find the schematic?

Does applying 5v to the 5v pin on the expansion dock have the same effect as applying 5v to the micro USB port? I am enclosing an Omega in such a way that there is not room for a USB cable connection. I could buy a bare micro USB plug and wire to that, but it will be easier if I can just apply 5v to the header. I didn't find a schematic to see if the expansion dock pin is simply a pass-through of the USB power or if I'll end up on the wrong side of a regulator.

My post didn't show up as I intended. I meant to suggest adding

">> $HOME/greeting.log 2>&1"

to the cronjob. The ">>" messed up the formatting.

Add

$HOME/greeting.log 2>&1

or some other file to the cronjob to capture any error messages. If this file does not get created, then the crontab failed to execute. If the file is created, then the job was executed and the file might contain some useful information about why you didn't get the expected result.

You can google the 2>&1 part for an explanation.

On a command line, ifconfig returns information that includes the WiFi connection.

Do you need something that is fully Json compliant, or something to work on simple key-value pairs. I wrote the following. It has worked, but no guarantees.

use: json json-string key default

json(){
a=$(echo "$1" | sed -E 's/[{}]/,/g; s/ *([:,]) /\1/g; s/"//g' | grep -oE ",$2:[^,]")
if [ -z "$a" ]; then
echo "$3"
else
echo "$a" | cut -d : -f 2
fi
}

I'm not near an omega right now so I'm working from memory. I found that I could avoid the resource busy message by using a system call from Python to execute a gpioctl command for control of an output pin. That side-steps the Python library.

OK, but these things are marketed for internet-of-things. For that, I imagine them to be embedded into a range of devices distributed around the house. Distributing surge protectors seems unattractive. The $15 power dock is probably not worth protecting with a surge protector. What concerned me more was that the device didn't just get bricked. It got hot enough to burn into a wood table top. If there is a fire hazard, then the failure impact is much greater than the replacement cost.

I had a Omega2+ running on a Power Dock. During a period of high wind, the power in my house went off briefly 5 or 6 times. This resulted in the Power Dock frying itself and putting a burn mark in the wood table top on which it was sitting. The power was supplied on the USB by a switching supply rated for input between 100 and 240 V. The device on the Power Dock that burned is the battery management chip near the four white LEDs. The Omega survived. I don't have a question on this. I just wanted to make everyone aware that this can happen.

On a related note, I had noticed previously that the Omega would sometimes stop running when power was supplied to the Power Dock on the USB connector while the Omega was running on battery power. I didn't do a lot of investigation of this but the common fact between that behavior and the burning up that I experienced is applying 5 V power when running on the battery. Has anyone else had problems switching back and forth between battery power and 5 V USB power?

Can you be more specific about what you are trying to do and how you would like this to work?

I posted a bit too soon.

The simpler commands (without the dbclient) work if the .ssh file contains a symbolic link to id_rsa. Execute this in the .ssh folder and things work more simply than what I suggested above.

ln -s id_rsa id_dropbear

I was having trouble making rsync work without the password request. I played with the file permissions as suggested in this and other posts. The advice was not all consistent so I tried different combinations, but nothing worked to eliminate the password request. I found a post (https://www.snbforums.com/threads/dropbear-ssh-without-remote-password.21070/) that showed how to specify the location of the private key. That worked.

This command results in a password request.
rsync -av -e ssh <source> <user>@<host>:<destination>

This command does not result in a password request.
rsync -av -e "dbclient -i /root/.ssh/id_rsa" <source> <user>@<host>:<destination>

Similarly,
ssh -i ~/.ssh/id_rsa <user>@<host>
will get me logged in without a password, while
ssh <user>@<host>
will request a password.

It sounds like it is possible to avoid the password request without explicitly pointing to the private key file. Others have done it but I failed on that score. Here is something that worked for me.

Where is it described what elements of the full python installation are not included in the python light installation? Python light is recommended because of its smaller footprint, but I didn't see a description of what is being missed in exchange for the smaller footprint. Sorry if I overlooked a section of the documentation.