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Gamepad decoder DTMF

Thanks to the MT8870 chip, connecting the outputs of STQ, Q4, Q3, Q2 and Q1 to a transistor allowing to open or close the buttons of a GAMEPAD, DTMF tones can be decoded. We only ineed 5 pins (control buttons). It has been created as proof of concept a simple program in VB6 (to work in old equipment W95) to be able to read the buttons and translate it to DTMF tones. The program is not optimized, so send the tones slowly. You can use the web generator
Can be tested with Windows’ own joystick tester

The concept is very simple, being the most difficult part in the manualities, to leave the control well prepared. The MT8870 can be powered with the 5 volts of usb, which we can take out following the cables of the control with a mulitester. The mass follows the same concept. The buttons of the controls, usually join 2 circuits, leaving the mass in common. To be sure we will look with a multitester the mass. What we are interested in is soldering the part of the button that is not mass. That part will go to the transistor collector. Since masses are common, we don’t need to weld all those parts. At the base of each transistor, we must connect a resistance of 100 Ohms, as protection. The transistor is worth any NPN, in particular I have used the 2N3904, which is the simplest and cheapest to get. Each output of the MT8870 (STQ, Q4, Q3, Q2 and Q1), goes to the resistance of 100 Ohms, and this in series goes to the base of the transistor (2N3904), while the collector joins it to the part of the button of the control that we want to activate and the emitter to the mass of the control.”

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