Casio Computer Rebuild Puts New Wine In An Old Bottle

With a glut of vintage consumer electronics available from eBay it should be easy to relive your glory days, right? Unfortunately the march of time means that finding gear is easy but finding gear that works is not. So was the case when [Amen] acquired not one, but two used calculator/computer units hoping to end up with one working device. Instead, he went down the rabbit hole of redesigning his own electronics to drive the Casio QT-1 seen here.

Especially interesting is the prototyping process for the replacement board. [Amen] used a “BluePill” STM32 microcontroller board at its heart, and used point-to-point soldering for the rest of the circuitry on a rectangle of protoyping board. That circuit is non-trivial, needing a 23 V source to drive the original VFD from the computer, a battery-backed real-time-clock (MCP7940), and a GPIO expander to scan the keys on the keypad.

It worked great, but couldn’t be cut down to fit in the case. The solution was a PCB designed to fit the footprint of the original. The modern guts still need more firmware work and a couple of tweaks like nudging that 23 V rail a bit higher to 26 V for better brightness, but the work already warrants a maniacal cry of “It’s Alive!”.

This isn’t [Amen’s] first rodeo. Back in March we looked in on another vintage Casio refurb that sniffed out the display protocol.

8 thoughts on “Casio Computer Rebuild Puts New Wine In An Old Bottle

  1. I will have to get mine out of it’s bank-check box and see if it works. Memories, like day-date computer any year. When a calculator had time based apps. Smart-calc, back when phones had carbon mics and weren’t owned.

  2. It’s a Casio CQ-1(it literally says it in the title of the blog post by Amen), not a “QT-1.” From what I can tell, the Casio QT line is a series of POS terminals, and their model numbers start in the low thousands, not at 1.

  3. A few years ago the Blue Pill costed around EUR3 and it was a very nice board.
    Now prices have dropped to below EUR 2 and the platform has been thorouhly demolished by one of at least 8 different (with incompatibilities and such) xxx32f103c8t6 manurefacturers, and the extra “re” is no typo.

    When you buy a “Blue Pill” from China, it always has the “STM” prefix, but it’s not a STM chip, but one of the others, with re-lasered top. If you want to preserve your sanity, you’d better look elsewhere for some better alternative.

    Die foto’s on Zeptobars and Richis-lab, and a long thread on EevBlog:
    https://www.eevblog.com/forum/microcontrollers/cheap-bluepill-very-likely-it-has-fake-stm32-right/?all

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