ACSI2STM: Atari ST Hard Drive Emulator
I bought an ACSI2STM adapter but haven't put it into a machine yet. It's a hard drive emulator for the Atari ST built around an inexpensive STM32 microcontroller and an SD card, an open-source project by retro16.
What it does
ACSI2STM connects to the ACSI (DB19) port at the back of the Atari ST and emulates a hard drive. It can work in three ways:
- Mount SD cards, standard SD/SDHC/SDXC cards (FAT16/FAT32/ExFAT) appear on the Atari.
- Expose raw SD cards as ACSI hard disks connected to the Atari.
- Expose disk image files as hard disks connected to the Atari.
It also provides an UltraSatan-compatible real-time clock if you add a simple 3V lithium battery such as a CR2032.
Hardware
The hardware is a custom PCB that can be ordered preassembled directly from JLCPCB. The board attaches straight to the DB19 port at the back of the ST and has three microSD card slots, with the firmware supporting up to five SD card readers. It's designed to be easy to build, extremely cheap, reliable and safe for the vintage machine. The project is mature and considered finished, with both software and hardware complete. It can even work on STs with broken DMA chips using the PIO firmware.
My Setup
I bought an ACSI2STM adapter, but it isn't in use anywhere yet, so it sits among my other uninstalled extensions. The UltraSatan currently provides the ACSI hard-disk storage on the "Low" machine, so the ACSI2STM would be an alternative or a spare for another machine.
Gallery
The ACSI2STM adapter, not yet installed.