Wifi Printing to HP Envy 4500 printer chops off top of page

If you are printing from Ubuntu Linux to an HP Envy 4500 printer and try to print a document with a very small top border, you may find that the printer chops off the very top quarter inch of the page.

The fix I found was to change the paper size from “US Letter (11 x 8.5)” to US Letter Borderless (11.14 x 8.72)” in the print drivers.

I have read several places online where other users with Mac’s and Windows machines have the same issue when printing over wifi, so I feel the issue is with the printer itself (and it’s wifi to printing bridge) as opposed to the Linux drivers.

30 second delays in internet on AT&T U-verse 5268AC FXN modem

My wife and I were running into inexplicable “delays” in our AT&T internet service over WiFi. The speed of the internet would be fine when it worked (speedtests showed good lag/upload/download, etc…) but sometimes the entire internet would “pause” and not respond for 20-30 seconds at a time. Usually not enough time for a connection to time out, but websites would be stuck loading for a long time, or Google Web Apps wold have a “loading….” message for half a minute before recovering (or failing to recover, making us try again with an edit to a document or calendar item…).

After much gnashing of teeth, network profiling, and dark vodoo, we traced the problem down to our devices auto-switching between the 2.4 Ghz and 5 Ghz wifi networks from the router [a Pace DSL modem Model 5268AC FXN ].  The problems happened most frequently when we had about 50% wifi signal strength to the 5G radio, and apparently our devices would see the stronger signal strength on the 2.4 router and switch over to it, then decide to switch back, and so forth.

The root cause of the problem is that the AT&T Uverse DSL gateway / wifi router has both networks with the same SSID (Name) and password, so our devices felt that they were “the same” network, just on different frequencies, and would switch between them frequently.  I have no idea why this would cause a delay of TCP/IP traffic, as a change in the physical/data link layer shouldn’t affect the Network/Transport layers (at least, not for 30 seconds).  Perhaps when using a different brand/model of Wifi Router devices can auto-switch between 2.4 and 5g seamlessly. ( Or perhaps not, our previous cable modem from Spectrum / BrightHouse named the two networks differently (with a 2 and 5 suffix) so that once you connected to a particular network frequency, you stuck with it, but at least we didn’t see this type of issue. )

In any case, the solution was simple. For testing purposes, we fixed the BSSID (mac address of the router) in our client devices to the 2.4 Ghz network, so it would not switch to the 5 Ghz radio. This fixed the problem.  Renaming the 5 Ghz network name to something different from the 2.4 Ghz network on the router would also have the same effect for all devices (for example, using myNetwork2.4 and myNetwork5 as the names).

Installing an Encrypted Partition with LVM dual boot on Ubuntu 16.04

The Ubuntu 16.04 installer has the option to install full disk encryption using LVM if you are erasing everything on the hard drive. However, if you want to dual boot (use some of the hard drive for Windows, and the rest for Linux) the automated installer won’t allow you to automagically use full disk encryption.

You can still make it work, but have to do a lot of manual work using a terminal from the Live CD environment.  Here is a log of what I had to do to get it working for me.

Continue reading

Flashing Kids Shoe Teardown

I took apart one of those kids shoes that flashes to see what the battery/circuit/sensor looked like. Here it is:

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img_20160920_113118

A small coin cell (under the round sticker), a circuit board, and a spring sensor are embedded in a square block of resin. It has three output channels (labeled R,G,B, although in this particular shoe all three were connected to red LED’s).  One LED (shown) was pointing out the back of the sole, and the other two were on top of the shoe. It took me about 5 minutes with a razer knife to dig this out of the sole of the shoe, and another 5 minutes to cut out the wires that went up to the red LED’s on the top of the shoe. Here is a video:

MicroMill Mach3 / LinuxCNC conversion complete

I have mounted the parallel port break out board inside the enclosure of my ScanTek 2000 (Denford Micromill). I routed the parallel port cable out to the previous DB25 (RS-232) outlet on the case and sealed up the back.

bob_mounted

With the built in wire management trays, the job looks almost professional…except for the fact that I used a triangular piece of 1/4″ acrylic scrap I had for the mounting plate, so I had to orient the break out board at an angle. But since it’s inside the case, nobody can see it anyways. bob_mounted_closeup

 

parallel_port_cable_inside_panel

Outside the case, the only visible difference is that I took off the black “RS-232” sticker that used to live next to the DB-25 connector. Continue reading

Ubuntu 14.04 Zoneminder PPA not showing images or videos in the web console

When you use the Ubuntu package manager to install Zoneminder on Ubuntu 14.04 using the PPA, one configuration line defaults to the wrong path. This prevents the web console from showing you videos or events, although if you configure a camera it will capture pictures from it correctly and show you them in the Zone editing tools.

Specifically, under Options->Paths you need to change PATH_ZMS to:
/zm/cgi-bin/nph-zms

(adding the /zm to the front).

Error log messages look like the following:

ERR [socket_sendto( /var/run/zm/zms-299592s.sock ) failed: No such file or directory]

One other issue that could cause similar behavior is not having mod-cgi enabled in apache.

Making Thunderbird send messages in the background (like Outlook)

My work recently changed over to using Office365.com for their email. As long as Office365 supports IMAP and SMTP (it does) I don’t mind so much, as I can continue to use Thunderbird on my desktop to access my email.

However, because the mail servers are no longer located “on-campus” the lag to the SMTP server is much more noticeable than before. When I pressed the “Send” button, Thunderbird would sit there for 20 seconds with a progress bar sending the mail, interrupting my flow of email processing much more noticeably than when the server was hosted on the same network.

So I tweaked a few advanced settings in Thunderbird by going into Thunderbird Preferences (Edit->Preferences), clicking the “Advanced” tab, then selecting the “config editor” button and promising to be careful.

mailnews.show_send_progress false
mailnews.sendInBackground true
offline.send.unsent_messages 1

Telling thunderbird to not show the progress indicator only hides the dialog, but the compose window still sits up on your screen (with no visible indicator of what it’s doing) until the mail is sent, so you also need to turn on “sendInBackground” to make the compose window disapear immediately after you press send.

This makes the message go immediately to your Local Folders -> Outbox, but DOES NOT SEND IT, until you select File -> Send Unsent Messages. Hence the “offline.send.unsent_messages 1” which tells Thunderbird to send unsent messages (from Folders -> Outbox) whenever it can. It still takes 20-30 seconds for the message to be sent, but it is done in the background now.