Hacking the Zsun WiFi SD Card Reader

The goal of this project is to learn as much as possible about the Zsun WiFi card reader and run OpenWrt on it to turn it into an awesome wifi device.

Hacking the Zsun WiFi SD Card Reader

UPDATE 2017-09-12 Info about LEDE and USB gadget working
UPDATE 2016-11-28 Adding some more info about the new PCB revision, thanks to Erik Dorner, who sent me his analysis a long time ago
UPDATE 2016-04-23 The new PCB is missing a jumper on the RX serial line, see serial port section
UPDATE 2016-03-16 The second PCB revision has identical software and hardware (apart from optimized minor component layout), flashing works the same
UPDATE 2016-03-12 We now know that there are at least two different PCB versions of the reader!
UPDATE 2016-02-21 github mirror at https://github.com/Emeryth/openwrt-zsun
UPDATE 2016-01-27 informatic seems to have figured out how to use the original firmware’s update function: Zsun Card Reader Firmware Update Format

People Involved

  • emeryth (emeryth at hackerspace.pl) ← contact me about the project
  • q3k (q3k at hackerspace.pl)
  • informatic (informatic at hackerspace.pl)

Current status

All the important aspects of hardware are understood.
OpenWrt Chaos Calmer ported (but not yet thoroughly tested), can be flashed over telnet if you dare.

What can I do with it?

  • Use it for its intended purpose of serving files, duh
  • Use as a tiny and pretty good WiFi AP/client/repeater (the hardware supports multiple simultaneous wireless interfaces!)
  • Play around with OpenWrt
  • Use it as the brains of your IoT project
  • Buy a dozen and play around with mesh networking
  • Use it for distributed WiFi activism like PirateBox or OccupyWiFi, or run a minimal Tor hidden service (with addition of being easily hidden in public places)
  • Host Node.js on it and take your apps to your favorite coffee shop :^)


  • AR9331 SoC
  • 64MB RAM
  • 16MB SPI Flash
  • GL827L USB SD Card Reader

The device consists of two PCBs sandwiched together and connected via 8 pins.
WARNING There are at least 2 PCB revisions, our original research was on the “old” revision, the “new” revision appeared in early 2016. The new revision has optimized layout with some minor changes, software is identical.

The bottom PCB contains only the SD card reader chip and SD slot, it can be safely removed without affecting operation. This is only true for the old PCB revision! The new revision moved the 3.3V regulator to the PCB with the card reader.

Serial Port

The serial console is brought out on testpoints (see pictures). Bitrate is 115200.

Original firmware root password is “zsun1188”

The new PCB has a missing jumper that connects the serial RX testpad to the SoC. Short it or solder directly to the lower pad of the jumper to use serial. (The second missing resistor is a pull up/down, I guess)

Read more: Hacking the Zsun WiFi SD Card Reader

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