The purpose of this project is to control a computer remotely by connecting directly to the ATX motherboard power IO control. The control will be done with Home Assistant by using ESPHome firmware.
Custom software could be written by using ESP-IDF SDK but it is not the purpose of this project.
Double 2.54mm pin headers are set for each ATX functionalities to manage:
PWR SW: ATX power buttonRST SW: ATX reset buttonPWR LED: ATX power state LEDHDD LED: ATX HDD activity LED
Two status LED are available:
PWR: 3.3V stateSTAT: System status controlled by software
Two buttons are available for ESP32 boot sequence:
BOOT: Control processor download mode on bootEN: Control processor reset
For advanced debug, the following connectors are available:
- 2x5 1.27mm pins header JTAG/SWD for external probe
- 4-pins Molex connector for UART
This project is based on an ESP32-C3 module to simplify design and ensure good WiFi performance (with external antenna connector). ESP32 has been selected for the big community to generate software and the frameworks available. Espressif hardware design rules has been take into account following there documentation
For easy debug and flashing, ESP32 with USB-CDC and JTAG support has been selected. It allows to remove the USB-UART bridge of the previous design.
The optocouplers for electric isolation have been selected following the PiKVM project experience. In the DIY PiKVM V2 instructions, the OMRON reference is recommended. Others relays/optocouplers may not be sensitive enough or low-level controlled.
The 3.3V to power all the components is generated from an LDO using the 5V of the USB socket. It can also be powered from external 5V on pins header. Both external 5V and USB can be connected at the same time, a power MUX is used to switch between both sources.
All others components has been selected from JLCPCB catalogue to minimize the cost and the assembly fees.
The board is manufactured by JLCPCB, here is the details you will require to generate an order.
Note: JLCPCB requests some modifications on output files, do not use direct export from KiCad (check the FAQ)
Files: Gerbers
| Configuration | Value |
|---|---|
| Base Materiel | FR-4 |
| Layers | 4 |
| Dimensions | 76.56 x 25.10 |
| Different design | 1 |
| Delivery format | Single PCB |
| PCB thickness | 1.6 |
| PCB color | Green (other colors have fees) |
| Silkscreen | White |
| Materiel type | FR4-Standard TG 135-140 |
| Surface finish | HASL |
| Specify layer sequence | F_Cu / In1_Cu / In2_Cu / B_Cu |
| Impedance control | Yes |
| Layer stackup | JLC04161H-7628 |
| Via covering | Tented |
| Min via hole size/diameter | 0.3mm/0.45mm |
| Remove order number | Specify a location |
Note: All options have not been detail here, keep default value.
| Configuration | Value |
|---|---|
| PCBA type | Economic |
| Assembly side | Top |
| Tooling holes | Added by JLCPCB |
Verify "pick & place" orientations and positions on the web viewer
JLCPCB will add 2 tooling holes for assembly (1 mm diameter near the board corners).
Note: All options have not been detail here, keep default value.
For those who want to reuse this project, here is the ESP32 pinout to manage the different input/output.
| Name | Pin | Direction |
|---|---|---|
| System Status LED | IO8 | Output (strapping pin) |
| ATX Power Button | IO0 | Output |
| ATX Reset Button | IO1 | Output |
| ATX Power State | IO3 | Input |
| ATX HDD Activity | IO10 | Input |
Device must be setup via USB connection the first time to flash the customized firmware with sensors/buttons configuration.
Once it has been configured successfully, you should fix the device IP on your router for easier Home Assistant configuration.
Note: Installation can be bypassed if already done or you can use docker image. Check ESPHome documentation for more details.
pip install esphome
# Ensure your user session has the correct permission for serial port.
sudo usermod -a -G dialout <USERNAME>Depending of your installation and network, a secrets.yaml file must be
create with your specific configuration.
# secrets.yaml
hostname: MyControllerHostname
wifi_ssid: MySSID
wifi_password: MyStrongPassphrase
wifi_fb_ssid: ATX Controller Fallback Hotspot
wifi_fb_password: StrongPassphrase
ota_password: MyOTAPassphrase
api_key: 32BytesBase64String# Generate the firmware.
esphome compile esphome.yaml
# Flash the firmware to the ESP.
esphome run esphome.yaml
# Get logs.
esphome logs esphome.yaml