My project is an audio pre-amp circuit with the following features:
The project is composed of a digital-controlled analog tone control chip and digital-controlled analog attenuators that perform the analog processing. Relays are used to select among the sound sources. A MC68HC11E1 microcontroller is used to control the analog processors and the LCD display. Control input is from push-button switches mounted on the front panel and from the infrared remote control.
The latest news (24 July, 1997) is that the system now works as intended. I did have some problems with the processor and bugs in the program that controlled the system. The problems with the processor include an instruction that didn't work (naturally, it was an instruction used for manipulating bits in a memory location, particularly the I/O ports) and documentation that omitted some details (for example, the program that programs the EEPROM cannot be executed from the EEPROM). The bugs in the code included the usual assortment of typos and logic errors. There were also some problems with the circuit design itself, particularly relays that didn't shut off and a signal from the infrared receiver that had to be inverted.
