The SW22 is deprecated. See the SW32 E-Stim for a better alternative.
This project is a work in-progress. Changes to the design might occur. Order PCBs at your own risk..
The SW22 is a modular E-Stim box based on the ZC95 and the WT-312. It has a similar form factor and output design to the MK312-BT (which in turn is a clone of the ET-312B).
An ESP32 module is used for high level control (front panel controls, display, Bluetooth audio, etc) of the device, while an RP2040 microcontroller (RPi Pico) is used as a co-processor for pulse/routine generation (taking advantage of PIO). The firmware is open source and written in C.
Compared to the MK312-BT, it has two extra output channels, four auxiliary inputs, and four triggers.
- Bluetooth A2DP*
- RS232 front panel serial
- 2x TRS 3.5mm Aux channels with expansion board support (e.g. Stereo Audio + Mono Microphone, RS232 Remote)
- 2x TRS 3.5mm Trigger channels
- Tri polar (+, GND, -) output channel support
- Modular output drivers per channel (Think: Sparkfun, Adafruit, etc.) incl. modular driver board.
- Individual channel sensing via quad 12-bit ADC
- 1.8" Color TFT display
- Support for an internal 0.96" I2C OLED display (e.g. debugging/testing)
- 256kb EEPROM for configuration
- Battery voltage monitoring
- Charge sense (Barrel jack voltage monitoring)
The SW22 consists of following PCBs:
- Front Panel Cover - No traces, just the cosmetic front panel with text. Could be 3D printed or laser cut.
- Front Panel - I2C based expansion board with 4x POTs with associated ADC, 1x rotary encoder, 4x tactile buttons, 1x buzzer, and 8x addressable RGB LEDs.
- Base Board - Provides system power, battery charging, expansion, Bluetooth, front panel interface, and general control.
- Driver Board - Provides low-level control over channel output modules.
- Output Modules - Generates the E-Stim for each channel. A module per channel, controlled by the driver board.
- Expansion Module (Optional) - Allows advanced configuration of Aux channels (e.g. Audio+Microphone)
The main reason for having modular PCBs is for flexibility and long term cost saving. Most of the cost and time that is involved in the project is the firmware, case, display, controls, etc. So being able to reuse parts when changing the design (e.g. new output modules, driver board, etc) should help keep time and cost down.
Additionally, the SW22 was designed with the front panel and display being optional accessories. Anything that can be achieved on the front panel, can be done via Bluetooth/WiFi. The driver board can be used as a standalone module (Think: Sparkfun, Adafruit, etc.).
The majority of this build is SMT. I have tried to keep parts large enough (0603 and above) for manual pick and place. However, for a few components, no alternative was available (e.g. Driver board uses MSOP/VSSOP packages).
Most SMD components used are available from Mouser and LCSC. Front panel components being mostly available at places that aren't LCSC (pots, encoders, audio jacks, etc).
Some components have a thermal pad that will require a reflow oven or using hot air reflow soldering.
Gerbers are created for use with JLCPCB. P&P POS files untested/missing (since I assemble the PCBs myself).
The firmware is open source and written in C. You can find the source code in the swef and swx repositories.
swef and swx don't support SPI used by the SW22 for connection between the base and driver boards. Basic functionality requires adding additional bodge wires (SDA and SCL) between the base and driver boards.
This change was done to simplify communications and to prepare for the successor SW32 box.