The HC-SR04 is a popular, and very inexpensive, ultrasonic ranging device and I'd like to modify one to change its functionality. If I can identify the controller I might be able to reprogram it, or at least replace it with one I can program myself.
The controller is a 14 pin SOIC and has pin 4 Vcc, pin 11 Gnd, Xtal between pins 5 and 6, and I think pin 7 might be a Reset. It has no markings at all on it, so the manufacturer obviously doesn't want me to know what it is.
The pinout doesn't seem to match any 14 pin PIC, or Atmel chip that I can find.
Is anyone familiar with this device or care to make an educated guess as to what the microcontroller might be?