LED debugging the stereowrap hardware

I found out earlier that 5V is not enough to drive the shutter glasses. With my breadboard setup for stereowrap, I fed 12V to the op amps from an external source. Now that I moved the thing to a strip board, I added a step up converter that generates 12V from the 5V available on the USB port. I used an LT1301 which comes with an application note for exactly my use case. It was easy to implement and worked from the first try.

Then I temporarily switched from an arduino duemillanove to a leo stick. Although it’s a tiny clone which plugs directly into an USB port, it still seemed like a bit of an overkill. I thought of using one of the AtTiny’s for that project. As I was not too familiar with these yet, I first did a hello world blinking LED’s. Soon after, I learned that neither the Attiny45 nor the AtTiny85 have a hardware UART. Well, I thought, there is an arduino software serial library. Arduino libraries are generally very easy to use in the IDE. But as I programmed the chip directly this time I wanted to stay within CodeBlocks/CMake and use the arduino library from here. Continue reading “LED debugging the stereowrap hardware”

payment slip reader

Probably the first time I got in contact with one of the pen style payment slip readers, was when I was working for TCG. They only come with drivers for Windows and in the meantime also for Mac. I contacted their support more than once, asking for a linux driver. No success so far. So I decided to get one cheap from ricardo.ch (similar to ebay.com). I was really lucky, and got one that makes noise when shaking for CHF 5. A new one would cost more than CHF 200. They have a very effective way of making sure people buy new ones from time to time. They just don’t release drivers for the older devices on newer versions of Windows. Well, that happens a lot in the Windows world, that people are forced to buy new devices. So there are a lot of devices floating around on ricardo.ch which only run on WindowsXP 32bit. Mine is one of those, but since I want to use it on linux that should be no problem.

When I first plugged it in, the USB id was recognized correctly:

$ lsusb
...
Bus 002 Device 010: ID 0a93:0002 C Technologies AB C-Pen 10

But that was about it.

Trying to capture the communication on the USB port worked nicely with WireShark under ubuntu. But as I had no driver for it, there was not much communication to monitor. So I had to capture on a Windows box. Not so easy in a Windows-free zone. I have a VMWare virtual machine on my harddisk that I used some time ago to maintain an ancient project. But the outdated WMWare-Player could not run with my current installation. I had to upgrade it. It compiled the kernel modules with some minor help. But then the VM wouldn’t boot. I suspect, they changed the hardware they emulate. That would be no problem with linux, but Windows has real trouble with changing hardware. That was the same reason, I could not migrate that VM to VirtualBox some years ago. So, I installed a new Windows VM with VirtualBox. But now I could not figure out how to make the USB device accessible to the guest OS. The next try was qemu. It’s not as point and clicky as the other two products, but it’s really powerful and comes with loads of features. I grow to like it ever more. Continue reading “payment slip reader”