Friday, August 28, 2015

Wireshark: Fixing "No interface can be used for capturing in this system with this current configuration." in Linux Mint and Ubuntu

I wanted to do a packet capture on a Linux Mint machine, so I opened a terminal and ran the usual command to install Wireshark.

sudo apt-get install wireshark

When I opened Wireshark, the section where you select which interface to capture from was blank and it said that "No interface can be used for capturing in this system with this current configuration."

Fortunately, the fix is easy. This worked for me on Linux Mint. It should work on Ubuntu as well.

Open a terminal and run:

sudo dpkg-reconfigure wireshark-common 

You should see a screen like the one below.

Answer Yes, then run this command:

sudo usermod -a -G wireshark $USER

Finally, reboot or log off and back on.

All the network interfaces should be listed now and Wireshark should function as expected.


Thursday, August 20, 2015

Adventures of a Comcast CableCARD Customer

TL;DR Version

If you're having trouble with your Comcast CableCARD, call (877) 405-2298 instead of the main 800 number.

The Full Story

I've had Comcast TV service for about a year and thought that I would share my experiences. I don't have a horror story like many Comcast customers, but my experience hasn't been without its headaches.

I started out just having internet service with Comcast. I dislike Comcast as much as the next guy, but the only alternative for internet access where I live is 6 Mb DSL from the local telco. No thanks!

One day, I got a phone call from Comcast. They had a promo going that would bump me up to a higher internet speed tier and included basic cable and HBO. This would end up costing less over a 2 year period, so I signed up.

They sent me a cable box that was SD-only and didn't have any DVR functionality. What is this? 1988?

Since I didn't want to pay to rent an HD-capable cable box, I picked up a SiliconDust HDHomeRun PRIME to use with Windows Media Center on my home theater PC. I called Comcast and told them that I'd like to turn in the cable box and get a CableCARD for my tuner. I was informed that they don't mail CableCARDs and that I would need to pick one up from a customer service center. The closest center was about 20 minutes away and in the opposite direction of work or anywhere else that I go with any sort of regularity.

I went to the customer service center and stood in line for about 30 minutes. When it was my turn, I told the representative what I needed and she said "no problem" and took the cable box and handed me a CableCARD from the shelf behind her. That was easy.

I went home, hooked the HDHomeRun and installed the necessary software to set it up. I called Comcast and went through the activation process and everything seemed to be working properly.

A little later, I noticed that HBO wasn't working. The basic channels worked fine, but I would get a "Subscription Required" message when I tried to watch HBO.

This was annoying, but not that big a deal since I only care about a couple shows on HBO and I generally watch them on HBO Go anyway. And frankly, it had been a long day and I didn't want to deal with Comcast anymore.

Several months later, I finally decided to quit being lazy and deal with my HBO issue. I called Comcast's main number and followed the prompts for tech support. The auto attendant started the inevitable barrage of attempts to prevent you from speaking to a human, such as the "did you know that unplugging cable box for a few minutes will solve most problems" and "let's send an automated reset signal to your cable box" prompts. After getting fed up and pressing 0 about 5 times the phone system finally relented and placed me in the queue to speak with a human.

After being on hold for about 3 minutes a representative picked up. I told her what was going on. She tried "resetting" and "re-sending the activation signal" to my CableCARD a couple times. During all this, I got some blinking lights on my tuner indicating that something was happening, but the issue persisted. After that, she arrived at the conclusion that premium channels aren't supported on CableCARDs and that I should go to a customer service center and trade the card in for a cable box. Yeah, no.

I hopped on Google to do some research since I clearly wasn't going to get anywhere with Comcast's main line. I found this post on DSL Reports where a user was having a similar issue. One of the replies contained the direct number to Comcast's CableCARD department - (877) 405-2298. I called this number and was transferred directly to a human. I explained what was happening and she told me that I called the right place and it would be no problem to fix this.

She checked my account and said that the card wasn't paired properly. In order to pair the card, she needed the Card S/N, CableCARD ID, Host ID, and Data (I'll go over where to find this information in the next section). I gave her this information and she paired the card. After the lights on my tuner stopped blinking, I tried HBO and it worked! The phone call took about 5 minutes. 

Comcast does employ knowledgeable people, but makes it difficult to get in touch with them. The moral of the story is if you're a Comcast customer with a CableCARD issue, call (877) 405-2298 and not the main line.

Getting CableCARD Pairing Information

If you need to pair a CableCARD, there are a couple ways to get the necessary information to give to your cable company.

If you're using an HDHomeRun PRIME, you can get the information through the HDHomeRun Config GUI program. Open the program and under the Webpage tab, go to CableCARD Menu > CableCARD(tm) Pairing. This will display the necessary information.

You can also get this information in Windows Media Center. This will work regardless of what tuner you're using.

In WMC, go to Tasks > Settings > TV > TV Signal > Activate Digital Cable

You'll be asked if you want to set up WMC for use with a CableCARD. Say Yes and go to the next screen.

Next, you'll see the message below. Click Next.

The next screen will display the information that you need to give your cable company.

Wednesday, August 5, 2015

USB to Serial (RS-232) Converters - Not All Are Created Equal

Integrated Serial Ports: A Dying Breed

Unfortunately, new computers with integrated RS-232 (aka serial) ports are getting harder and harder to find. These days it's next to impossible to find a new laptop with an integrated serial port, and they're quickly disappearing from new workstations. While this is of of little consequence to most end users, many IT professional need a serial port on almost a daily basis.

Most people who need a serial port, myself included, deal with this by using a USB to serial converter. I've used numerous converters over the years and had varying levels of success. Generally speaking, the manufacturer of the converter itself doesn't really matter. What's important is the chipset that the converter uses. Most converters I've come across use a Prolific PL 2303 chipset. Avoid these like the plague!

I've run across numerous driver issues when working with Prolific-based converters, although this seems to have gotten better lately. Even with a working driver, these converters are still problematic. While I've found Prolific-based converters will generally work okay if all you're using them for is console access to something using a terminal emulator program, they cause all kinds of problems when you're using them for anything more complex, such as connecting to ham radio interfaces or GPS devices.

A Tale of Two Converters

A while back, I had a customer who had some Windows Mobile-based scanners that were used to read water meters. The scanners used a cradle with a serial interface to import the data into their software. They were constantly getting errors and losing connectivity when importing the data and would often have to attempt the transfer 5-6 times before it would succeed.

They finally got fed up and brought me in to troubleshoot. I checked the back of the cradle, and they were using a USB to serial converter. I opened the device manager and checked the properties for the serial port. Sure enough, the converter that they had purchased (from the manufacturer of the scanner, no less) had a Prolific chipset.

I swapped out the Prolific-based converter for one with an FTDI chipset (more on this in a moment), and all their problems miraculously vanished. This is one of many stories I have where issues with a serial device were caused by a Prolific-based converter.

FTDI Chipset

A number of years ago I discovered the FTDI chipset and haven't looked back. They are compatible with Windows, Linux, and Mac, and in my experience they work just as well as integrated serial ports.

Some of the FTDI-based converters that I have. They all work equally well.

While FTDI-based converters tend to be a little more expensive than their Prolific-based counterparts, the cost difference is negligible in the long run. So if you're in the market for a USB to serial converter, do yourself a favor and get one that is based on the FTDI chipset.

Sunday, August 2, 2015

ATI/AMD Catalyst 15.7.1 Drivers on Windows 7 Can Break HDMI Audio

Last night, I sat down to watch some TV that I had recorded with Windows Media Center on my trusty Windows 7 home theater PC. When I tried to play the recording, I got an error saying that "The video decoder is not working, is not installed, or is not supported." What?!

Windows Media Center Decoder Error

I tried rebooting. No dice. Some quick googling indicated that this error may be audio-related. At this point I realized that I wasn't getting any audio from the PC. No menu sounds in WMC, no audio when I played an mp3, nothing.

I checked the sound properties and confirmed that the HDMI Output was set as the default playback device.

When I went into the HDMI Output properties and tried to test the device, I got an error saying that the device was being used by another application. This error persisted even after a reboot. Weird.

This is when I remembered that the night before I had updated the AMD Catalyst drivers for the Radeon HD 6450 in that machine from 15.7 to 15.7.1. I didn't catch the issue at that time because I had gone to bed immediately afterwards.

I went into Programs and Features and told AMD Catalyst Install Manager to do an express uninstall of all AMD software.

After that, I reinstalled the 15.7.1 drivers. The issue persisted. Next, I repeated the uninstall process and rolled back to the 15.7 drivers. Everything worked properly after that.

Your mileage may vary, but you may want to skip 15.7.1 if you're running an AMD graphics card on a Windows 7 machine that relies on HDMI audio.