Dmitry Grinberg’s rePalm challenge, which goals to port Palm’s basic Palm OS platform to trendy {hardware}, has reached a brand new milestone: the power to run Palm OS 5 on a Raspberry Pi Pico or different RP2040-based growth 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 (a minimum of in principle) for [Arm] Cortex-M0, I wished 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 working at 133MHz and 264kB of static RAM (SRAM). It is this RAM which might show the largest problem: “The final Palm OS machine to have this little RAM ran Palm OS 1.0,” Grinberg explains. “If I wished to make use of the complete 320×240 show in true-color mode, the framebuffer would occupy 150kB. Oof! Nicely, how a lot IS acceptable?”
With just a little experimentation, Grinberg was capable of pare down the RAM necessities to 231kB for the underlying working system and storage, leaving 33kB for the framebuffer — which itself was then pared all the way 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 shade depth. (📷: Dmitry Grinberg)
“There’s nonetheless lots to do: implement BT [Bluetooth], Wi-Fi, USB, debug NVFS [Non-Volatile File System] some extra, and possibly many extra issues,” Grinberg admits. “Nonetheless, I’m releasing some little preview pictures to strive, when you occur to have an STM32F429 Discovery Board, an AximX3, [or] a Raspberry Pi Pico with the correct display.”
Extra particulars, and a hyperlink to obtain the software program, is on the market on Grinberg’s web site.
