ZBM-MG dongle IO configuration
For stock images, use Flash USB dongle firmware. You do not need these pins.
The I/O below is for custom firmware: building your own coordinator / router / Thread image, porting another project, or writing a flasher. Match UART, BOOT, reset, and how the USB-serial chip drives auto-download.
This page covers ZBM-MG21 / ZBM-MG24. ZBT-1P follows the official SkyConnect pinout (not listed here). Its USB chip is in the last table for comparison.
Pins
Both boards wire USART to USB-serial without hardware flow control. BOOT is active-low. NRST is driven by the DTR / RTS circuit, so you do not press reset by hand while flashing.
| Item | ZBM-MG21 | ZBM-MG24 |
|---|---|---|
| Silicon | EFR32MG21A020F768IM32 | EFR32MG24A420F1536IM40 |
| USART TX | PB01 | PC01 |
| USART RX | PB00 | PC02 |
| Flow control | None | None |
| BOOT | PA00 (active-low) | PC00 (active-low) |
| RESET | NRST, via DTR / RTS | NRST, via DTR / RTS |
| LED | None | None |
| Baud (recommended) | 115200 | 115200 |
When you bring up custom firmware:
- Do not swap TX / RX, and do not move USART to other pins unless the board wiring changes too
- Do not enable RTS / CTS on this UART; those lines are not wired to the radio
- Prefer 115200. If you change baud, match the flasher and the ZHA / Zigbee2MQTT serial settings
Auto-download
The USB-serial chip uses DTR and RTS to drive NRST and BOOT, so the web flasher and the Windows tool can enter boot without shorting the BOOT pin.
Truth table (1 / 0 are DTR and RTS levels):
| DTR | RTS | NRST | BOOT |
|---|---|---|---|
| 1 | 1 | released | released |
| 0 | 0 | released | released |
| 1 | 0 | reset | released |
| 0 | 1 | released | enter boot |
Drive DTR / RTS this way in your own downloader: enter boot, then send the image over USART. Do not toggle these lines during normal serial traffic, or the stick will reset or sit in boot.
USB serial
Driver links are in Flash USB dongle firmware. Custom scripts can key off VID:PID:
| Product | USB chip | VID:PID | Typical node |
|---|---|---|---|
| ZBM-MG21 | WCH CH343 / CH9102 | 1a86:55d4 | /dev/ttyACM0 |
| ZBM-MG24 | Silicon Labs CP210x | 10c4:ea60 | /dev/ttyUSB0 |
| ZBT-1P | CP2102N (same as official ZBT-1) | 10c4:ea60 | /dev/ttyUSB* |
ZBM-MG24 and ZBT-1P share a VID:PID. Do not tell them apart by USB ID alone; use the enclosure or the model the user selected.
To flash official firmware only, use USB dongle model flasher. You do not need to drive these I/O lines yourself.