/Gamepad

Primary LanguageAda

Gamepad Project

Project

The Gamepad project is a project made by a 4-people team. The goal was to create a gamepad from a STM32-F4 board, to be able to play games through USB. However, the project is still unfinished. This project is divided in two parts. One is the gamepad in itself, and the other is a USB stack to transmit informations. All code is written in ADA.

How to build it

In order to build the project you just have to follow the two next steps, once the card is plugged to your computer.

  • gprbuild --target=arm-eabi -d -P prj.gpr -XLCH=led =XRTS_Profile=ravenscar-sfp -XLOADER=ROM -XADL_BUILD_CHECKS=Enabled src/main/adb -largs -Wl,-Map=map.txt
  • st-flash obj/main 0x80000

Behaviour

The command are sent generated using the gyroscope of the card. On launch, the user will see a target on the screen of the card. This target contains all the information for the user to send data to the computer. In fact, the cursor is the orientation, and the colors are the command being sent. When the sensor is tilted forward, The Z keycode is send, backward S keycode, to the left with Q and to the right with D. We can mix two keycode like Z and Q by going in diagonal. Each color corresponds to a command and a modifier status key.

  • White smoke: no movement, all keycode to NONE.
  • Green: Orientation + Left Ctrl modifier status key.
  • Yellow: Just the orientation
  • Red: Orientation + Left Shift

The data are then sent through USB, if USB is connected, or through UART. The UART part is working fine, however, you may have trouble using the USB stack as it is incomplete.

Development informations

Gamepad

The Gamepad uses an in-board L3GD20 gyroscope and the driver from ADA driver library. To reduce the drift, at the beginning, the average of zero motion raw data of the gyroscope is computed. For each raw data given, the average is removed and data are filtered through a high-pass filter from W3C Working Group Note for Motion Sensors. With this fixed angular velocity, a discrete integration is done with initial value to 0°. From the tilt of the board, some keycode is added to a report as explained above (In the "behaviour" part). The report format is the same as USB keyboard . An 8 length bytes message with the first byte being a bitfield of all modifier status key (Left/right Ctrl, Shift, Alt, GUI), the next one is a reserved byte and next 6 byte, an array of the key pressed. When there is a change (a new key is pressed or a key is released) the report is sent through UART with transmission pin at PA9 and reception pin at PA10.

USB Stack

In order to use the gamepad with a computer, or any other device, it is necessary use a USB Stack and register as an HID controller. Nevertheless, there is no such stack in the Ada Driver Library. One of the aim of this project was to add this stack. This work is compiling for now but does not do a thing. It is based on Fabien Chouteau's prototype. We took what was present and added some part in our implementation. We did not have much time left on debug. So we keep our implementation with transmission via UART. Nevertheless, we think about seeing afterwards to make this stack work and make it, if possible, integrated in ADA Drivers Library, as it was really interesting for our group to work on it.

Contracts

In order to have good control over our code, we chose to write contracts for our Gamepad functions. Those contracts can be found as Pre and Post conditions, but also Predicates and asserts. This is useful for us because it documents and tests our code at the same time.

Authors