Tab5 PC

A PC emulated on the M5Stack Tab5, built on tiny386: a 386/486 with VGA, a PS/2 keyboard and mouse, a Sound Blaster 16, AdLib and PC speaker, IDE hard disks, CD-ROM images, floppies and SeaBIOS. It runs DOS and Linux. On an empty SD card it downloads and installs FreeDOS or Sprig Linux by itself; files are copied to it over Wi-Fi from a browser.

This is an independent project, not affiliated with or endorsed by M5Stack. It is provided as is (see LICENSE).

What you need

• An M5Stack Tab5 (ESP32-P4). The Tab5 Keyboard is recommended; a USB keyboard and mouse work too.
• A microSD card, FAT32 or exFAT, with at least 1 GB free.
• A Wi-Fi network with internet access for the FreeDOS download (or prepare the card on a computer, below).

To build the firmware:

• Arduino CLI with the M5Stack board package (m5stack:esp32, from https://static-cdn.m5stack.com/resource/arduino/package_m5stack_index.json) and the libraries M5Unified, M5GFX and lvgl. Built and tested with m5stack:esp32 3.3.10, M5Unified 0.2.29, M5GFX 0.3.0 and lvgl 9.6.0.
• git, curl, make, tar with xz, a C compiler, xxd, and the GitHub CLI (gh, logged in: gh auth login) for tiny386's BIOS images.
• Python 3: python3 -m venv .venv && .venv/bin/pip install -r requirements.txt. Run the tools with .venv/bin/python (tools/make_sdcard.py and tools/dosdisk.py also find .venv by themselves).
• Optional: dosfstools (fsck.fat; brew install dosfstools on macOS), with which tools/make_sdcard.py and tools/dosdisk.py check the disks they write.

Ready-made firmware

Each release has the firmware as one image to write at address 0 (tab5-pc-<version>-prev3.bin, for the Tab5's ESP32-P4, revision v1.x), with its licenses and notices and the corresponding source. Releases have no image for ESP32-P4 v3.x while no Tab5 with that chip is out (see below to build one). It is also in M5Burner. To write it yourself: esptool --chip esp32p4 write-flash 0x0 tab5-pc-1.6.0-prev3.bin.

Build and flash

tools/fetch_vendor.sh            # tiny386 at the pinned commit (with the patches in vendor/patches),
                                 # its SeaBIOS images (the BIOS built here), and ESP-Hosted's SDIO driver
tools/build.sh upload            # build and flash (port /dev/ttyACM0; or: tools/build.sh upload /dev/ttyACM1)

The BIOS (SeaBIOS) is built from the pinned source with tiny386's patch, as vendor/patches/0027 changes it (it reports the math coprocessor), and the VGA BIOS comes from tiny386's release; both are checked against the tested images pinned in vendor/bios.lock. Building the BIOS needs a gcc that can build 32-bit x86 code (on Debian or Ubuntu, gcc-multilib). BIOS_FROM_SOURCE=1 tools/fetch_vendor.sh builds the VGA BIOS from source too.

ESP32-P4 chips come in two families: esptool reports "revision v1.x" for earlier ones (the default build) and v3.x for later ones: CHIP=postv3 tools/build.sh upload. A build for the wrong family does not start.

First start: FreeDOS on an empty card

1. Put an empty card in the Tab5 and switch it on. With nothing on the card, the settings panel opens with Wi-Fi on: choose your network on the right, then tap DOS in the Machine frame and give the machine a name (for example dos; tap again to confirm). The Tab5 restarts into its install mode, with no PC running, and shows how it goes. (Linux sets up Sprig Linux instead, and ISO a PC that starts from an installer CD on the card: see More machines.)

   

2. The Tab5 downloads FreeDOS 1.4's LiteUSB disk (18 MB, from freedos.org), makes the PC's hard disk (/dos/C.IMG, 512 MB, partitioned and formatted) and the machine's settings (/tiny386-dos.ini), and restarts into FreeDOS's own installer. Answer its questions: your language, Yes to proceed, Yes to format the drive (the installer calls it D:, as it started from its own disk), your keyboard, Plain DOS system, and Yes to install. (The questions that default to No need Up, then Enter.)

3. Copying the packages takes about 20 minutes. When the installer asks to reboot, say yes: the Tab5 sets the machine up to start from its C.IMG alone, removes the installer's files from the card, and adjusts C:\FDAUTO.BAT for this PC (its CD-ROM driver; the Sound Blaster's BLASTER setting). FreeDOS then starts at the C:\> prompt.

   

Other ways to start:

• An installer CD: the Machine frame's ISO (below), or by hand: put the .iso of a bootable installer CD (for example FreeDOS's LiveCD) on the card, make an empty hard disk (.venv/bin/python tools/dosdisk.py new sdcard/C.IMG --mb 500, copied to the card) and write a tiny386.ini with hda = /sdcard/C.IMG and cdc = /sdcard/<name>.iso (see Settings). The BIOS tries the hard disk first, so the PC starts from the CD while C: is empty, and from C: once a system is installed on it.
• Prepare the card on a computer: .venv/bin/python tools/make_sdcard.py makes sdcard/C.IMG (FreeDOS 1.4 with all its packages, 32 MB), sdcard/D.IMG (504 MB, empty) and a matching sdcard/tiny386.ini. Copy the three files to the root of the card. It starts straight at the C:\> prompt.

More machines: DOS and Linux side by side

The settings panel's Machine frame lists the machines on the card: default (/tiny386.ini) and every one named N (/tiny386-N.ini, its files in the folder /N). Choose one and tap Start twice: the Tab5 restarts into it, and keeps starting it, through every restart, until you choose another.

DOS, Linux and ISO install a new machine (DOS and Linux are downloaded: a saved Wi-Fi network is needed): give it a name, tap again to confirm that the PC stops, and the Tab5 restarts into its install mode, with no PC running, then into the new machine.

• DOS: FreeDOS 1.4, as above: its installer starts in the new machine.

• Linux: the latest release of Sprig Linux, a small Linux made for this PC (about 10 MB downloaded, 140 MB on the card), every file checked against the release's checksums. It starts with a graphics console (800 x 600); the machine's settings file says how to use the text console instead. Installing Linux again with the same name updates it: its kernel and loader are replaced, its disk (root.img, your files) is kept. (Its start is the picture at the top of this page.)

• ISO: a PC that starts from an installer CD. Copy the CD's .iso to the root of the card first (the web page's SD card tab), then choose it in the dialog (the machine's name is suggested from it). The new machine gets an empty hard disk (C.IMG, 512 MB, partitioned and formatted) and the CD in its drive; it starts from the CD while C: has no system, and from C: once the installer has put one there. The CD stays in the drive until the CD-ROM tray (see Using it) takes it out.

A name already on the card (its settings file or its folder) can't be used again, except to update Sprig Linux. If an install fails, the screen says why, and a tap goes back to the machine there was. Serial: machines, machine <file>, install dos <name>, install linux <name>, install iso <name> [<file>.iso].

Using it

The Tab5 Keyboard. Aa, Ctrl and Alt are the PC's Shift, Ctrl and Alt. Sym is a layer (never sent to the PC):

Sym +	gives		Sym +	gives
1 ... 0	F1 ... F10		← → ↑ ↓	Home, End, Page Up, Page Down
- and +	F11, F12		Backspace	Delete
Del	Insert		Aa	Caps Lock
the symbol keys	their second symbol		Esc	the settings panel

Ctrl + Alt + Delete is Ctrl + Alt + Sym + Backspace. Sym + Alt + Up/Down sets the speaker volume. The left light shows Sym or Aa held, the right one is green while the PC runs. Docked in the keyboard, the picture is turned to match.

USB. A keyboard and mouse in the Tab5's USB-A port (also through a hub, or a wireless receiver) work alongside. Scroll Lock opens the settings panel.

The touch screen is a touchpad for the PC's mouse: slide to move, tap to click, tap with two fingers for the right button, tap and touch again to drag. DOS programs need a mouse driver (CTMOUSE, which FreeDOS loads).

The side panels beside the PC's picture, as on a PC's case: on the left POWER (hold it a second: the PC is off; tap it: on again, starting afresh; the PC also goes off when its system powers it off, e.g. FreeDOS's FDAPM POWEROFF), RESET (hold it a second), PAUSE (the PC's picture dims and stays still, the sound stops) and SETUP (the settings panel); on the right the power light (green on, amber paused), the disk light (amber; both dim when off, as a real LED's lens), the CD-ROM tray, a camera (screenshots) and the battery (red when low). A ring fills around POWER's or RESET's icon while you hold it; a short tap on either does nothing while the PC runs.

Screenshots: tap the camera and the PC's picture is saved on the card in screenshots/, as a PNG named by the day and that day's count (2026-11-05_001.png), at the picture's own size (640 x 400 for 80-column text, 320 x 200 for a 256-colour game, 800 x 600 for Sprig Linux's console ...). The camera's flash lights up, then its light shows green for a moment (red: not saved, the card full or missing). The day comes from the Tab5's clock (it keeps UTC), in your time zone: opening the Tab5's web page sets both from your browser, and while you have Wi-Fi on, the Tab5 also checks the time with an internet time server (pool.ntp.org) every 3 hours. Over the serial console, clock shows the time, clock 2026-11-05 18:30:00 sets it (UTC) and clock tz PST8PDT,M3.2.0,M11.1.0 the time zone, as a POSIX TZ string. Serial shot takes a screenshot too.

The CD-ROM drive: every machine has one, empty unless its settings file names a disc. The tray shows the disc's name; tap it for a dialog listing the .iso files at the root of the card (1 MB or more) and No disc: Insert or Eject changes the disc while the PC runs, as with a real drive (FreeDOS notices within a few seconds; dir on an empty drive says it is not ready). The disc is saved in the machine's settings file, so it is still in the drive at the next start. Serial: cd shows the disc, cd <file>.iso inserts one, cd - ejects it.

Sound: the PC speaker, the Sound Blaster 16 (BLASTER=A220 I5 D1 H5 T6) and AdLib play through the Tab5's speaker.

Copying files over Wi-Fi

Wi-Fi is off until you switch it on. Open the settings panel (swipe down from the top edge, Sym + Esc, or Scroll Lock) and switch on Copy files over Wi-Fi. The Tab5 joins your network and shows its address, e.g. http://192.168.1.50/. Open it in a browser:

• The SD card tab lists the card: disk images, CD images (.iso), tiny386.ini. Drop files or whole folders anywhere on the page to copy them. Edit opens text files (tiny386.ini, .BAT, CONFIG.SYS, ...); after saving tiny386.ini the page offers to restart the Tab5 with it.
• The C: and D: tabs open the PC's disks. This pauses the PC (DOS keeps parts of its disks in memory). When you press Done, or 30 s after the last change, the PC continues, restarted if anything changed. Do this at the DOS prompt, not while a program is saving.
• The images the PC has open can't be changed while it runs: Delete on one offers to stop the PC first (like switching it off). It stays stopped until Start PC restarts the Tab5.
• Long file names are stored with DOS short names (LONGNA~1.TXT).
• From a shell: .venv/bin/python tools/upload.py <address> hdb /APPS ~/dos/myprog, then .venv/bin/python tools/upload.py <address> --done.

Switch Wi-Fi off again when you are done. The Tab5 keeps the choice: after a restart or a power-off, Wi-Fi comes back on or stays off as you last left it.

The file manager has no password. Anyone who can reach the Tab5 on the network can read, change and delete everything on the card and the PC's disks while it is on. Switch it on only on a network you trust, and never make it reachable from the internet (no port forwarding, no exposed host).

The PC's network

The PC's network card (NE2000, port 300h, IRQ 9) is connected to a small network inside the Tab5 (192.168.77.0/24; the Tab5 at .1 hands out addresses by DHCP and answers DNS queries by passing them on to your Wi-Fi network's DNS server). While Wi-Fi is on, it is routed to your Wi-Fi network with address translation, as a home router does; with Wi-Fi off, the PC still gets its address, and its lookups fail at once. The PC reaches your network and the internet; from your network, ports 2222, 2323 and 8080 of the Tab5 lead to the PC's 22, 23 and 80 (an SSH, Telnet or web server running in it). DOS needs a packet driver for the NE2000 and a TCP/IP program; serial net shows the card's state. The same warning applies: anything the PC serves on those ports is open to your network.

For example with FreeDOS's NE2000 packet driver (Crynwr's NE2000.COM) and mTCP (DHCP, ping, FTP, Telnet, HTTP client and server, IRC, time), both free software, in C:\NET with an MTCP.CFG that says PACKETINT 0x60:

C:\NET\NE2000 0x60 9 0x300
set MTCPCFG=C:\NET\MTCP.CFG
C:\NET\DHCP
C:\NET\HTGET -o PAGE.HTM http://example.com/

The graphical browser MicroWeb (built for mTCP, run from its own directory) shows plain-HTTP pages; most of today's web needs HTTPS, which these programs don't do.

Settings

The settings panel (swipe down from the top edge, Sym + Esc, or Scroll Lock; Done or Esc closes it): pause or reset the PC (reset asks for a second tap), Wi-Fi for copying files and the network list, brightness, volume, the touchpad's speed, the side panels on or off (off: the margins are black and part of the touchpad; the picture is always 4:3, as on a monitor, text and 320 x 200 graphics stretched to the full height), and the machine to start or install (More machines). The top right shows the battery. While the panel is open the PC keeps running.

tiny386.ini at the root of the card describes the machine (or tiny386-N.ini, the machine named N, if it is the one chosen in the panel); the Tab5 reads it when it starts:

key	meaning
[pc] hda ... hdd	hard disk images, e.g. hda = /sdcard/C.IMG
cda ... cdd	CD-ROM images (.iso)
fda, fdb	floppy images (1.44 MB etc.)
mem_size, vga_mem_size	memory, e.g. 16M, 2M
fill_cmos	1: the hard disks' geometry in the CMOS
bios, vga_bios	other BIOS images on the card (the built-in SeaBIOS otherwise)
vga_force_8dm	0: text in the VGA's 9-dot cells (720 x 400); 8 dots wide otherwise (640 x 400, no stripes in shaded backgrounds)
[cpu] gen	3, 4, 5, 6 = 386, 486, 586, 686
fpu	1: an x87 maths coprocessor

Without a cda-cdd line a machine still has a CD-ROM drive, empty, as cdc (cdd if hdc is taken); the CD-ROM tray writes the disc it inserts into this file. FreeDOS installed with Tab5 PC 1.3.0 or earlier has a rem before the CDROM.BAT call in C:\FDAUTO.BAT (its CD-ROM driver): delete it to use the drive.

More disks: .venv/bin/python tools/dosdisk.py new sdcard/E.IMG --mb 1000 makes an empty one (hdc = /sdcard/E.IMG); dosdisk.py put and ls copy files in and list them on the computer.

The serial console (USB): .venv/bin/python tools/console.py "S" prints the status; tools/shot.py out.png saves the PC's screen (--panel: the Tab5's). Commands are listed at the top of firmware/tab5_386/tab5_386.ino (e.g. wifi on, vol <0-255>, reset, type <text>).

Performance

The PC is roughly as fast as a 486 of the early 1990s for typical DOS programs: simple integer instructions run at about 20-30 million a second. A fast interpreter in front of tiny386's own handles the common instructions, and a translator turns frequently run code into RISC-V code (real, virtual-8086 and protected mode, paged or not). The x87 runs in software, with single precision on the ESP32-P4's FPU where that gives the same result. Text and EGA/VGA programs draw at up to ~30 frames a second; only what changed on the screen is redrawn.

Notes from the development are in docs/NOTES.md.

Licences

This project's own code and documentation are under the MIT License (LICENSE). The exceptions in this repository are LVGL's configuration template (lv_conf.h, MIT), the Tab5 Keyboard's key table from M5Stack's M5Unit-KEYBOARD (MIT, in keyboard.h), the parts of the CPU code adapted from tiny386 (BSD-3-Clause), and the patches in vendor/patches, which contain tiny386's code (BSD-3-Clause, and MIT for its QEMU-derived files) and ESP-Hosted's (Apache-2.0). Their notices and full license texts are in THIRD_PARTY_NOTICES.md and LICENSES/.

The firmware is built from more than this repository. The tools fetch these, and they are not kept here:

• tiny386, the emulator core, at a pinned commit. It is mixed-license: BSD-3-Clause as a whole, MIT for the parts that come from QEMU/TinyEMU, BSD-3-Clause for inih, and LGPL-2.1-or-later for the FMOPL AdLib synthesiser, which this firmware compiles in.
• SeaBIOS and its VGA BIOS (LGPL-3.0), pinned in vendor/bios.lock and built into the firmware.
• ESP-Hosted's SDIO driver (Apache-2.0).
• The Arduino core for ESP32 (LGPL-2.1) with ESP-IDF (Apache-2.0 and others), M5Unified and M5GFX (MIT), and LVGL (MIT, with fonts under the SIL OFL).

A compiled firmware image therefore carries obligations of its own (notices, corresponding source, LGPL relinking). No binaries are published here; docs/DISTRIBUTION.md lists what is needed first. FreeDOS (GPL and other free licences) is downloaded by the Tab5 or by tools/make_sdcard.py from freedos.org; it is not part of this project.

M5Stack and Tab5 are trademarks of their owner; other names are trademarks of their respective owners.