2020-04-12 10:39:24 +02:00
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+++
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date = "2020-04-11T00:00:00+02:00"
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2020-05-23 20:36:04 +02:00
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title = "Self-contained and smoke"
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2020-04-12 10:39:24 +02:00
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highlight = true
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draft = false
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2020-05-23 20:36:04 +02:00
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tags = ["kieferbot"]
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2020-04-12 10:39:24 +02:00
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+++
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A day of highs and lows. Here's Kieferbot still in [teleop][teleop]
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mode but now self contained:
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<video controls src="self.m4v"></video>
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The [PinePhone][pinephone] is taking commands from a PS4 DualShock
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over Bluetooth using `ds4drv` and sending them to the IO board over
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serial. I experimented with a few transports:
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- UDP over Wifi was fine, but the default ESP32 Wifi power mode added
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random latency of up to 100 ms. Switching to 'always on' mode by
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modifying MicroPython fixed this.
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- Bluetooth Low Energy worked for one-way communication to the IO
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board, but there was lots of packet loss when using Bluetooth for
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both the joystick and IO.
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Inspired by [Firmata][firmata], I settled on MIDI over serial. I
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quite like the MIDI format for short messages. A frame starts with
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the command followed by a command specific payload. The command has
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the MSB set so it's simple to frame.
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I also compiled [ROS Kinetic][kinetic] for Debian Buster and created an IO node
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that takes left and right velocity commands. There seems to be an
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ordering issue with either the ESP32 PWM chip or the FIT0441
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controller, where going from forward to reverse and vice-versa is
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fine but the motor won't start sometimes when going from zero.
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So plenty of highs, but the low was [releasing the smoke][smoke] - I'm
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using a LiPo battery for the supply and something short-circuited when
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unplugging the battery. It seems to have taken out the regulator and
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the ESP32 flash.
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Next step is to re-make the IO board using an [ItsyBitsy M4][m4]. It
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also runs MicroPython so the IO software was easy to port. I've
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ordered some Seeed [XIAO][xiao] boards - $5 gives you a MicroPython
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compatible SAMD21 with 9 pins of IO which is enough for this project.
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This time I'll secure the battery socket better and 3D print a
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shield.
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[pinephone]: https://wiki.pine64.org/index.php/PinePhone
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[teleop]: https://en.wikipedia.org/wiki/Teleoperation
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[firmata]: https://github.com/firmata/protocol
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[xiao]: https://www.seeedstudio.com/Seeeduino-XIAO-Arduino-Microcontroller-SAMD21-Cortex-M0+-p-4426.html
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[kinetic]: http://wiki.ros.org/kinetic
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[smoke]: https://en.wikipedia.org/wiki/Magic_smoke
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[m4]: https://www.adafruit.com/product/3800
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