Dmitry Grinberg’s rePalm challenge, which goals to port Palm’s basic Palm OS platform to fashionable {hardware}, has reached a brand new milestone: the power to run Palm OS 5 on a Raspberry Pi Pico or different RP2040-based improvement board, making intelligent use of the chip’s programmable enter/output (PIO) capabilities.
“How little RAM/CPU does Palm OS 5 actually require? Since rePalm had assist (at the least in principle) for [Arm] Cortex-M0, I needed to strive on actual {hardware}, as beforehand the assist was examined on CortexEmu solely,” Grinberg writes in a challenge replace delivered to our consideration by Adafruit. “There does occur to be one Cortex-M0 chip on the market with sufficient RAM — the RP2040, the chip within the $4 Raspberry Pi Pico.”
The RP2040 is a dual-core low-cost microcontroller that includes two Arm Cortex-M0+ cores operating at 133MHz and 264kB of static RAM (SRAM). It is this RAM which might show the largest problem: “The final Palm OS gadget to have this little RAM ran Palm OS 1.0,” Grinberg explains. “If I needed to make use of your entire 320×240 show in true-color mode, the framebuffer would occupy 150kB. Oof! Effectively, how a lot IS acceptable?”
With a little bit experimentation, Grinberg was in a position to pare down the RAM necessities to 231kB for the underlying working system and storage, leaving 33kB for the framebuffer — which itself was then pared right down to a 320×240 decision at 4 bits per pixel, or 160×160 at eight bits per pixel.
To get a full-resolution show in simply 264kB of RAM required a four-bit grayscale colour depth. (📷: Dmitry Grinberg)
“There’s nonetheless so much to do: implement BT [Bluetooth], Wi-Fi, USB, debug NVFS [Non-Volatile File System] some extra, and possibly many extra issues,” Grinberg admits. “Nevertheless, I’m releasing some little preview photos to strive, if you happen to occur to have an STM32F429 Discovery Board, an AximX3, [or] a Raspberry Pi Pico with the right display.”
Extra particulars, and a hyperlink to obtain the software program, is on the market on Grinberg’s web site.