While running https://github.com/fhoedemakers/pico-infonesPlus, I found that my SNES gaming pad was not fully supported.
Specifically the UP DOWN and LEFT RIGHT keys were not working.
Let's debug this a bit:
Plug in the gaming pad on a Linux box and run the following command (hidraw5 will need to be changed as needed):
$ sudo hexdump -C /dev/hidraw5
...
00004a50 01 80 80 7f 7f 0f 00 00 01 80 80 7f 00 0f 00 00 |................|
00004a60 01 80 80 7f 00 0f 00 00 01 80 80 7f 00 0f 00 00 |................|
*
00004a80 01 80 80 7f 7f 0f 00 00 01 80 80 7f 7f 0f 00 00 |................|
This is what I see when pressing the UP key.
The byte pattern at byte 5 position is changing (00 to 7f pattern).
Let's check the pico-infonesPlus code for handling NES / SNES controllers:
$ vim pico_shared/hid_app.cpp
...
(r->byte7 & MantaPadReport::Button::START ? io::GamePadState::Button::START : 0) |
(r->byte7 & MantaPadReport::Button::SELECT ? io::GamePadState::Button::SELECT : 0) |
(r->byte2 == MantaPadReport::Button::UP ? io::GamePadState::Button::UP : 0) |
(r->byte2 == MantaPadReport::Button::DOWN ? io::GamePadState::Button::DOWN : 0) |
(r->byte1 == MantaPadReport::Button::LEFT ? io::GamePadState::Button::LEFT : 0) |
(r->byte1 == MantaPadReport::Button::RIGHT ? io::GamePadState::Button::RIGHT : 0);
The existing code is checking for changes at byte 2 position instead of byte 5 position!
To get UP DOWN keys to work, we can simply apply the following patch:
- (r->byte2 == MantaPadReport::Button::UP ? io::GamePadState::Button::UP : 0) |
- (r->byte2 == MantaPadReport::Button::DOWN ? io::GamePadState::Button::DOWN : 0) |
+ (r->byte5 == MantaPadReport::Button::UP ? io::GamePadState::Button::UP : 0) |
+ (r->byte5 == MantaPadReport::Button::DOWN ? io::GamePadState::Button::DOWN : 0) |
Similarly we can debug other gaming pad keys as well.
Sample controller image:
References: