The white version of the TinyRobo board that has the missing ground trace also doesn’t have a proper connection for the pullups on the I2C address lines for the motor drivers. The drivers are still there, and scanning the I2C bus with a Bus Pirate (Amazon) showed me that they were at 0x63 and 0x64 on the I2C bus, rather than where I expected them to be (at 0x66 and 0x68). The difference is consistent with a connection that should have been to Vcc being left open.
I’m not wild about the problem, but it did give me an opportunity to set up and use Pulseview/Sigrok, my cheap clone logic analyzer, and my Bus Pirate, so it’s not a total waste.
For my own future reference, as well as anyone else who’s interested, the way to set up the Bus Pirate on Ubuntu is this:
- Plug it into a USB port
- Open up a terminal and type screen /dev/buspirate 115200 8N1 , where /dev/buspirate is whatever device your bus pirate ended up on. Mine was /dev/ttyUSB0.
- The terminal will go blank. Hit enter, and you should get the “HiZ>” Bus Pirate terminal.
The I2C bus scan is run by hitting “m” to get the menu, “4” to get I2C mode, “3” to set speed to 100kHz, and then “(1)” to run the scan macro.
The cheapo logic analyzer I got is a USBee & Saleae clone, which I got because I’m
bad and should feel bad not rich. It has a switch to determine which device it claims to be. In Saleae mode, Sigrok loads an alternate firmware onto it, so I’m not really sure where that falls in the intellectual property/doing the right thing by small businesses framework, but if you can afford one, get a proper USBee or Saleae. They’re much better built (the Saleae Logics in particular are tanks) and have more and better features.
I’m doing all this stuff in Enschede, at U. Twente. I’ve been hanging out with the people in the HMI group, which “does things with stuff”. They do a lot of work with things like proxemics in interaction, socially aware robots and technology, and so forth. There’s something of a distinction here between technical stuff, which is what I do a lot of, and more abstract work with avatars and such. I’m a better fit with the RaM (Robotics and Mechatronics) group, which builds things like pipe-crawling robots and quadcopters.