I dug this out **broken link removed**
Parking, but not brake is probably coast.
TTL logic tends to float high, so in a lot of cases, one uses NOT Enable, so when you disconnect the controller from the motor driver, the motors don;t start running. Processor pins come up in a high Z state and therefore you don't want the motor to move until you have control.
Here's **broken link removed** a much simpler interface, but it won't do for your motor. There's no harm in bringing up the datasheet:
https://www.st.com/content/ccc/reso...df/jcr:content/translations/en.CD00000240.pdf
The Canakit has a sense resistor, so you can monitor current. One resistor for both directions. You don't want a roque wheelchair or one that can chop off a limb. Motors draw a big spike of current when they start. Current is proportional to torque. When you use this equation V=Vm-Im*Ra; Vm, you can't measure. Ra is the resistance of the armature. Im is the current through the motor. If you could measure Vm, it would be proportional to speed. That's the basis of a DC tachometer.
An issue with wheelchairs is quiescent power. The Arduino really doesn't have a lot of power management stuff. You may also have to deal with 3.3. and 5V interfacing.
Not really sure what the intention of a wheelchair brake is besides making the turning radius small when you brake one wheel or they use coast and brake to make things cheaper. Brakes can also be controlled with PWM. The brake is probably necessary when using a wheelchair lift.
I'm totally familiar with manual wheelchairs. Me pushing.
So, yea back to your project. With one wheel braked and turning the other, there would seem to be a max speed (PWM percentage) that could be determined. I'd use this as an initial max speed when doing full lefts and rights. You also have ramped starts to deal with. Seat belts? Must you be in the chair? Dead man's switch so to speak.
Then, there is the battery fuel gauge and charging circuits.
I'm throwing out ideas based on what I know without being familiar with an electric wheelchair. The closest thing is a motorized shopping cart.
On/OF with key, FWD/REV, a blinking light when the battery gets low, and a back-up beeper. You also have to be seated properly with no feet on the ground. I'm not sure how they make that happen. With a foot on the floor, it won't go.