Aquaplus - P/ECE (piece-emu)¶

Background¶

The P/ECE (pronounced "piece") is a handheld game console released by Aquaplus in Japan in 2001. It is built around the EPSON S1C33209 SoC (S1C33000 32-bit RISC CPU core) and has a 128×88 four-level grayscale LCD, a D-pad, A/B/START/SELECT buttons, PWM sound and a USB connection to a PC. Aquaplus published the development kit and the kernel source, so most P/ECE software is homebrew distributed by its authors as .pex application files.

piece-emu is a P/ECE emulator written in C++. It emulates the S1C33000 CPU, the S1C33209 on-chip peripherals, the LCD controller and the NOR flash, and boots the real P/ECE kernel from a flash image. The libretro core is part of the piece-emu project.

The piece-emu core has been authored by:

Autch

The piece-emu core is licensed under:

MIT

A summary of the licenses behind RetroArch and its cores can be found here.

Requirements¶

None.

How to start the piece-emu core:¶

The content for this core is a .pfi (P/ECE Flash Image) file: a complete image of the P/ECE flash memory that contains the kernel (system software) and the applications installed in the on-flash file system (PFFS). There is no separate BIOS.

A .pfi is not a per-title ROM. It is closer to the hard disk image of a computer core: the user assembles it, and a single image holds the system plus any number of applications. P/ECE applications (.pex) cannot be loaded as content directly; add them to a .pfi and start them from the P/ECE launcher. Everything RetroArch handles per content, such as the save file, playlists, and per-game remaps and option overrides, therefore applies to the whole image rather than to each application.

A .pfi can be made from a real P/ECE with the ripper tool, or built without the hardware from Aquaplus's official system updater:

Download update120.exe from the official PieceSystem 1.20 download page. It is an LHA self-extracting archive: run it on Windows, or extract it with lha x update120.exe elsewhere.
Build the image with the mkpfi tool from the piece-emu repository:
```
mkpfi -512kb piece/update/all.bin piece.pfi
```
Use mkpfi -2mb piece/update/2mb/all.bin piece.pfi for units modded to 2 MB flash.
Add applications (.pex) to the content with the pfar tool, for example pfar piece.pfi -a mygame.pex.

Then, in RetroArch, select 'Load Content', choose the .pfi file and, if asked which core to use, choose 'Aquaplus - P/ECE (piece-emu)'. The P/ECE launcher (menu) starts; pick an application from it.

BIOS¶

Not required. The P/ECE kernel is part of the .pfi content.

Extensions¶

Content that can be loaded by the piece-emu core have the following file extensions:

.pfi

RetroArch database(s) that are associated with the piece-emu core:

None

Features¶

Frontend-level settings or features that the piece-emu core respects:

Feature	Supported
Restart	✔
Saves	✔
States	✕
Rewind	✕
Netplay	✕
Core Options	✔
Memory Monitoring (achievements)	✕
RetroArch Cheats	✕
Native Cheats	✕
Controls	✔
Remapping	✔
Multi-Mouse	✕
Rumble	✕
Sensors	✕
Camera	✕
Location	✕
Subsystem	✕
Softpatching	✕
Disk Control	✕
Username	✕
Language	✕
Crop Overscan	✕
LEDs	✕

Directories¶

The piece-emu core's library name is 'piece-emu'

The piece-emu core saves/loads to/from these directories.

Frontend's Save directory

File	Description
*.srm	Flash memory contents (PFFS save data of every application in the image)

The loaded content (.pfi) itself is never modified. Everything the kernel and applications write to flash (high scores, settings, user data) goes to the .srm file instead, which is itself a complete PFI image: it can be inspected with pfar (pfar piece.srm -l), or renamed to .pfi to boot it as standalone content.

Once a .srm exists, the core restores the entire flash from it when the content is loaded, so the .srm, not the .pfi, becomes the live image. Applications added to the .pfi afterwards do not appear. To add an application at that point, close the content and either add it to the .srm (pfar piece.srm -a newgame.pex), or rename the .srm to .pfi and use it as new content.

Geometry and timing¶

The piece-emu core's core provided FPS is 60
The piece-emu core's core provided sample rate is 32000 Hz
The piece-emu core's base width is 128
The piece-emu core's base height is 88
The piece-emu core's max width is 128
The piece-emu core's max height is 88
The piece-emu core's core provided aspect ratio is 16:11 (128:88)

Usage¶

By default RetroArch writes the .srm only when the content is closed, so exit with 'Close Content' rather than killing RetroArch. Setting 'Settings → Saving → SaveRAM Autosave Interval' to a non-zero value also protects against losing data when RetroArch is killed.

Core options¶

The piece-emu core has the following option(s) that can be tweaked from the core options menu. The default setting is bolded.

Swap A/B Buttons [piece_swap_ab] (Off (RetroArch standard)|On (Swapped))

Off: RetroPad A is the P/ECE A button and RetroPad B is the P/ECE B button. On: the two are swapped.
Timer Tick Granularity [piece_tick_burst] (2000|3000|4000|6000|8000|12000|16000)

How often the emulated peripheral timers and interrupts are serviced, in CPU cycles. Larger values reduce the per-frame cost (raising the frame rate on slow hosts, such as RetroArch Web) but deliver interrupts more coarsely; if set too large, audio goes silent. 4000 runs at roughly the speed of the real P/ECE.

User 1 device types¶

The piece-emu core supports the following device type(s) in the controls menu, bolded device types are the default for the specified user(s):

RetroPad - Joypad

Joypad¶

RetroPad Inputs	User 1 input descriptors
	B Button
	Select
	Start
	D-Pad Up
	D-Pad Down
	D-Pad Left
	D-Pad Right
	A Button

With the 'Swap A/B Buttons' core option enabled, RetroPad A and B are exchanged.

Compatibility¶

The kernel boots and applications run with display, input, sound and flash saves. The following P/ECE hardware is not emulated yet, so applications that depend on it do not work or have reduced functionality:

USB
IrDA (infrared communication)
MMC card interface
ADC
IDMA