We have a number of Pixies and have experienced the following problem on all. We are using the Pixies on robots that follow colored objects. Each Pixy is connected to a custom PCB via an IDC cable. Pins 2 and 10 of the IDC connector power the Pixy and run to a Pololu dropdown voltage regulator that powers all the components on the PCB, including a Teensy 3.5 (which connects to the Pixy via SPI). (The robot is powered by a 3S LiPo.) The PCB has numerous other components on it, all of which are powered by the regulator. In our application, it is critical that we assign signatures using Pixymon rather than by pressing the button on the Pixy. We have noticed at times that, after we assign the signature in Pixymon, and the Pixy is clearly tracking an object, when we unplug the Pixy and turn on the Arduino, the signature doesn’t seem to have been saved on the Pixy. When we reconnect to Pixymon, we confirm this is the case. We are unclear as to what impact powering or not powering the PCB when we are teaching the Pixy objects using Pixymon has on this. We are running the latest firmware and version of Pixymon. We are wondering if you all understand what’s going on and if there are ways to avoid the problem. Thanks.
Hello Jonathan,
One issue that can arise is the white balance. By default Pixy will gather white-balance information in the first 5 seconds after power-up. If Pixy is in front of a colored object upon power-up, the white balance can be “off” (shifted) and the color signatures won’t typically work for that power cycle. It can look as if the signature that was working is no longer working. You can reset the the white balance by pressing Pixy’s button and holding a white piece of paper in front of Pixy. (see the white balance section on this page: http://cmucam.org/projects/cmucam5/wiki/Teach_Pixy_an_object_2) You can also use a fixed white balance (see the Camera tab) which will make sure that the white balance will always be the same regardless.
There have been reports of Pixys losing signatures because of power brown-out. If the power supply is having trouble supplying enough current to Pixy, the Pixy’s flash memory can malfunction. How much current can the Pololu voltage regulator supply at 5V? If it can’t supply more than 250mA, there may be issues. Pixy draws 160mA at 5V (nominall), so 250mA of potential current is a good margin.
Edward