What is difference between "using" and "by using"?

Sometimes both "using" and "by using" seem to have the same meaning. Am I wrong? For example, compare the sentences below:

• "On-screen keyboards allow people with mobility impairments to type data using a joystick or a pointing device."
• "On-screen keyboards allow people with mobility impairments to type data by using a joystick or a pointing device."

Both sentences use "using" for the same purpose, don't they? And their meanings are the same, aren't they?

Although it sounds correct and could pass without a glance, if you examine the logic of the sentences, they mean something slightly different.

An on-screen keyboard allows people with mobility impairments to type data using a joystick or a pointing device.

The first sentence states that people with mobility impairments use the joystick and pointing device in order to operate the on-screen keyboard.

An on-screen keyboard allows people with mobility impairments to type data by using a joystick or a pointing device.

By using a joystick or a pointing device, an on-screen keyboard allows people with mobility impairments to type data.

The second sentence states that the on-screen keyboard is the one that uses the joystick or pointing device to allow impaired people to type data.

The difference: In one of them, the people use the joystick in order to control the machine. In the other, the machine uses a joystick so that people can control it. Both of them are true in this case, but they aren't the same.