Salida

1. A linuxfrom scratch project (Using a Go bin as a userspace)
2. mp3 player
3. Linux phone (Mobile VOIP only to simplify everything?) Unlikely to get to this stage but whatever

Hardware

SoC: Allwinner T113-S3

• Dual-core Cortex-A7 @ 1.2GHz
• 128MB DDR3 (integrated in package)
• HiFi4 DSP for audio offload
• Integrated audio codec (ADC/DAC, I2S, DMIC)
• USB OTG
• QFN package — no BGA Modem: Quectel EC200U (LTE Cat 1, USB)
• Data only — voice and SMS handled over IP
• AT command interface
• Presents as standard network interface once connected Other: LiPo + AXP209 PMIC, SPI NOR flash (boot), microSD (storage), USB-C, 3.5mm audio jack, MEMS microphone, tactile buttons.

Software

Mainline Linux kernel with a custom board device tree. No init system, no package manager, no userspace beyond a single statically compiled Go binary. No cgo

The Go binary runs as PID 1. It mounts /proc and /sys, brings up the network interface, manages the modem via AT commands over serial, and handles all audio I/O through direct ALSA ioctls on /dev/snd/. No CGo — CGO_ENABLED=0, fully static.

Mainline Linux kernel + custom DTB
└── Go binary (PID 1, statically linked)
    ├── MP3 decode (go-mp3)
    ├── Audio I/O (/dev/snd/ via ioctl)
    ├── Input handling (/dev/input/event*)
    ├── Modem management (AT commands over /dev/ttyUSB*)
    ├── VoIP (Opus encode/decode, SIP or WebRTC via pion)
    ├── Messaging (Matrix or custom TCP/TLS)
    └── Networking (Go net package, DHCP, DNS)

Memory

128MB is the primary constraint. Go's GC allocates before collecting, so peak usage during VoIP or network bursts can spike well above steady state. If the process is OOM-killed and it's PID 1, the kernel panics.

Two mitigations are planned: a thin C init as PID 1 that restarts the Go binary on crash, and GOMEMLIMIT=96MiB to keep the GC aggressive. The T113-S3 hardware watchdog will reboot the device if the process hangs.

Boot Chain

Boot ROM → SPL → U-Boot → kernel + DTB → Go binary

OS lives on SPI NOR flash. User data on microSD. FEL mode (USB) available for recovery.

Building

# Kernel (cross-compile for ARMv7)
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- t113s3_defconfig
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- -j$(nproc)

# Go binary
CGO_ENABLED=0 GOARCH=arm GOARM=7 GOOS=linux go build -o handheld .

Daydreaming

• A headphone jack. (Why don't phones have these anymore?!?)
• Centrialized logging
• Home screen inspired by T-UI (android launcher https://f-droid.org/packages/ohi.andre.consolelauncher/)
• Scripting language like GDScript for programming anything with access to APIs for volume, gps, flashlight, ect.
• Intuitive sandboxing. Easily see app permissions and change them perminately.
• GUI/TUI framework (Idk what to do for this)
• A browser (I have no idea how this would work with so little ram. NetSurf?)