Dr. Scott M. Baker's Latest Boards Bring Music and Speech to Epson's Venerable QX-10 CP/M Micro
Dr. Scott M. Baker is back with another pair of boards designed to bring voice to esoteric vintage hardware, offering add-in cards for Epson's QX-10 CP/M microcomputer from the 1980s for sound and speech.
"I’ve been having fun with my Epson QX-10 — in the previous blog post I built a CompactFlash IDE storage device for it. But, the computer has four more expansion slots and I want to fill them out," Baker explains. "I figured I’d start simple. The AY-3-8910 is a popular sound chip for Z80 based systems."
So, step one: A sound card, designed to pop into the QX-10's expansion slot. The result is a simple board with the choice of taking its timing from the host QX-10 or using an on-board oscillator and which ties into a pre-existing audio playback package developed by Wayne Warthen for CP/M.
Music is one thing, but Baker has a passion for speech - having spent time earlier this year bringing the National Semi Digitalker back to life, throwing in a little Wi-Fi connectivity courtesy of an Espressif ESP32 microcontroller for good measure.
"I went a little bit different route on the speech board than on the sound board," Baker explains. "Rather than used a PLD [Programmable Logic Device], I used a good ol’ 74HCT688 magnitude comparator and a DIP switch. Set the DIP switches to off-off-on-off-off-off to place the speech board at its default address of 0xDC (right along side its friend, the sound board)."
"A 74HCT32 is used to combine the CS out of the 74HCT688 with the IO Read (IOR) and IO Write (IOW) strobes from the QX-10. For writing, we trigger the ALD pin on the SP0256 to load a phoneme off the data bus. When reading, we use a 74HCT244 to put the STB and LRQ signals onto D0 and D1. This allows you to write a phoneme to 0xDC, and then loop reading 0xDC and wait for D1 to go low."