We are going to make a nice control box with random buttons and potentiometers using the TI MSP430 LaunchPad. We want to be able to select an autonomous mode with a dial using one of the potentiometers through the LaunchPad.
The problem is, how do I send what the choice is to the robot if the LaunchPad is seen as a gamepad?
Should I write a pygame script and use pynetworktables to send the choice from it? Or is there a much simpler way that I am overlooking? How do other teams do it?
Why not simply use a multiposition button? They look like potentiometers but have different settings you can snap to rather than an analog output.
Apart from that, reading it as a joystick or just running some kind of direct voltage reading would work.
It sounds like he is worried that the robot won’t be able to read the joystick axis in autonomous since it is, well, autonomous. I don’t actually know if this is the case or not.
NetworkTables would work just fine for sending the choice. Alternately your code could read the joystick axis in a periodic function, or in disabled, and then use the value from there in autonomous.
At the beginning of autonomous, the FPGA latches the most recent joystick values received. So you can read joystick values in autonomous as long as you have set them properly before autonomous.
This. We have 5 rocker switches that we wired to buttons 1 through 5 on the Launchpad, and just read the button states at the beginning of autonomous like a boring old joystick. Easy and simple.
(our biggest problem has been with the physical construction of our wiring to the buttons coming undone - we should redo it)
You hit the nail on the head. I just wasn’t sure if I would be able to grab the latest value from the joystick, but it sounds like you can from the reponses. Thanks!
In the “old days” when the joystick values were all returned during autonomous as neutral with no buttons pressed, the typical tactic was for the user program to read and save the values while the robot was disabled before the match began, then use the saved values during autonomous. That is now done for you by the system.
My team was considering doing this. Would the TI LaunchPad Evaluation kitwork? Also, how would you make it work? Would you wire it to the RoboRio or to a different module?
If you’re open to an alternative method… We set our options this year by creating custom buttons/drop boxes on the dashboard. Our drive team would configure auto as required at the setup and network tables would sent the info to the robot. This can make things a tad simpler at times (we had at least three options to set this year).
We put a multiposition selector switch right on the robot. It’s a 12-position dial (with a nice solid click-click-click action) and a built in LED that lights up which position is selected. Internally it is a resistor ladder so you read it as an analog input on the RoboRio. Worked very well for us. The drive team literally dials in which autonomous they want to run before each match.
In one of the Launchpad example control panels I wired up an 8 position one. You can see it here to get an idea of how to do it: http://processors.wiki.ti.com/index.php/File:Mixed_Analog_Wire.JPG
The red and black wire on either end of the resistor chain are +3.3V and gnd, and the one in the middle is the signal out.
In response to using a TI LaunchPad-
It would be much simpler, at least in my opinion, to use a Raspberry Pi Zero, as it is so inexpensive and abundant. It can pretty easily pretend to be a joystick with as many buttons as you want, and will have a LOT more support from outside sources and forums due to its much larger user base than the TI LaunchPads.
Interesting and somewhat related side note- if I remember right from my tinkering with the Pi, the Driver Station pitches a fit if you have a joystick with more than 32 buttons/ axes/ pov’s combined, so keep that in mind when constructing your interface regardless of controller. You might have to double up on microcontrollers if you want anything incredibly complex.
Raspberry Pi runs Linux which means there is a significant boot time. If the usb cable were to come loose during a match, the last thing I want to be waiting for is the thing to boot up again.
That is quite a valid point…
However, it won’t be on the robot and uses only micro-b type connectors, which are latching (not locking, however), so it can withstand some abuse, but if you think it’ll be roughed around too much, then definitely pick the LaunchPad.
We really like it. You plug it right into an analog input on the RoboRio and just read the input voltage. The resistor network (similar to ILAMtitan’s second photo) is internal, and there’s a nice blue LED for visual feedback too. Plus, it’s cheap!
