### Running an analog clock backwards

I didn't think it was possible, but recently I came across this YouTube video and its associated blog post (in Japanese, which I was able to understand thanks to Google Translate):

Here's a diagram to contrast the pulses sent to the clock lines to turn the clock backwards, versus driving it forward:

As you can see, during the first time step, instead of sending a single positive or negative pulse, you send a short pulse, wait a little, then send a longer pulse in the opposite direction. Then in the next time step, a mirror image of the pulses in the previous time step is sent. The duration of the pulses has to be experimentally determined for different clock motions.

For example, I was able to use this follow code to move the second hand on my clock in a reverse motion reliably:

```int tickpin = 25;

void rtick() {
digitalWrite(tickpin, HIGH); delay(10);
digitalWrite(tickpin, LOW); delay(10);
tickpin = (tickpin == 25 ? 27 : 25);
digitalWrite(tickpin, HIGH); delay(30);
digitalWrite(tickpin, LOW);
}
```

So the short pulse is 10ms, the short wait is also 10ms. The longer pulse is 30ms.

Here is a video of the clock in reverse motion:

I was able to reverse-drive the clock reliably up to 4x speed using the code above. I pause the second hand after every 60 ticks, and noted where the stoppage point is. Then I let the code run overnight and came back in the morning to check that the second hand is still stopping at the same place.

But once I tried increasing the speed to 5x or 8x, slippages started to occur.

### Adding "Stereo Mixer" to Windows 7 with Conexant sound card

This procedure worked for my laptop (Thinkpad E530) with a Conexant 20671 sound card, but I suspect it will work for other sound cards in the Conexant family. I was playing with CamStudio to do a video capture of a Flash-based cartoon so that I can put it on the WDTV media player and play it on the big screen in the living room for my kids. The video capture worked brilliantly, but to do a sound capture, I needed to do some hacking. Apparently, there was this recording device called "Stereo Mixer" that was pretty standard in the Windows XP days. This allowed you to capture whatever was played to the speaker in all its digital glory. Then under pressure from various organizations on the dark side of the force, Microsoft and soundcard makers starting disabling this wonderful feature from Windows Vista onwards. So after much Googling around, I found out that for most sound cards, the hardware feature is still there, just not enabled on the software side. Unfortunately, to

### Hacking a USB-C to slim tip adapter cable to charge the Thinkpad T450s

This hack is inspired by this post . A year ago, I bought an adapter cable for my wife's Thinkpad X1 Carbon (2nd Gen) that allows her to power her laptop with a 60W-capable portable battery (20V x 3A). A USB-C cable goes from the battery into the adapter, which converts it to the slim tip output required by the laptop. Everything works out of the box, so I didn't give much thought about it. Recently, I decided to buy a similar cable for my Thinkpad T450s. I know technically it should work because the T450s can go as low as 45W (20V x 2.25A) in terms of charging (though I have the 65W charger - 20V x 3.25A).  I went with another adapter cable because it was cheaper and also I prefer the single cable design. So imagine my surprise when the cable came and I plugged it into my laptop and it didn't work! The power manager just cycle in and out of charging mode before giving up with an error message saying there is not enough power. After much research and reading the Thinkwiki