This Beautiful DIY Serial Terminal Features Vintage LED Bubble Displays

In the early days of digital computing, it was common to use terminals to interface with computers. While terminals often looked like computers on a superficial level, they usually weren’t capable of processing or running programs themselves. The purpose of a terminal was to provide input to a connected computer and to display the output. As it became more common for computers to have their own monitors and keyboards, hardware terminals were relegated to fairly niche applications. But they still have their purposes today, particularly if you are into retrocomputing. Mitsuru Yamada developed a 6802 serial terminal that features fantastic vintage LED bubble displays to interface with his own homebrew retrocomputer.

Like Nixie tubes and VFD (Vacuum Fluorescent Display) tubes, LED bubble displays are generally obsolete today. But they still possess tons of charm thanks to their unique aesthetic that you just can’t get from modern LCD or OLED screens. In this case, a total of 12 individual HCMS-2972 LED bubble display modules are built into the terminal. Each of those is able to display eight alphanumeric characters, with each character produced on a 5 x 7 LED dot matrix. The modules are arranged in a grid to produce a larger display that can show 24 x 4 characters. That isn’t a huge amount of text, but it is sufficient for most tasks that a serial terminal would be used for.

While most terminals are not computers, this particular design actually does contain hardware that technically makes it a computer. It is built around a Motorola 6802 processor, which was used for many computers in the ‘70s and ‘80s. It has 128 bytes of embedded RAM and is paired with 2KB of ROM. The RS232 serial interface is handled by a Hitachi HD6350 chip and the parallel interface is through a 74HC374 octal D-type flip-flop. The keyboard’s 48 keys, which are nifty-looking tactile buttons, are arranged in a standard 8 x 6 keyboard matrix. All of that hardware is housed within a sturdy die-cast aluminum enclosure. The entire terminal is about the size of a small paperback novel and can be powered by a battery pack. It is perfect for interfacing with the PERSEUS-3 homebrew 6502 computer that Yamada originally made way back in 2007.