$1.8 XT-ZB1 Zigbee & BLE devkit features BL702 RISC-V module

Bouffalo Labs BL702 is a 32-bit RISC-V microcontroller with a 2.4 GHz radio for Zigbee 3.0 and Bluetooth 5.0 LE connectivity that we first found in the Sipeed RV-Debugger Plus UART & JTAG debug board that did not make use of the radio at all.

But a BL702 development kit was brought to my attention, with the XT-ZB1 devkit equipped with a Zigbee & BLE module of the same name, and sold for just $1.80 per unit on Aliexpress. Shipping adds $4.63 where I live, but they also offer packs of 5 or 10 with the same shipping fee, meaning if you buy 10 the total cost should be around $22 including shipping, or around $2.2 per board. Alternatively, the module alone goes for $1.

XT-ZB1 Zigbee development boardXT-ZB1 devkit specifications:

  • XT-ZB1 wireless module with
    • MCU – BL702C 32-bit RISC-V microcontroller @ 144 MHz with FPU, 132KB RAM, 192KB ROM, 1Kbit eFuse
    • Storage – 8MB embedded flash
    • Connectivity
      • 2.4 GHz radio
      • 802.15.4, Zigbee 3.0, Bluetooth 5.0 LE with long range support, up to 2 Mbps bitrate
      • PCB antenna
    • Power Consumption @ 3.3V
      • Rx only – 3.5 mA
      • Tx – 0dBm: 4.9 mA, 10 dBm: 17mA; 14 dBm: 45 mA
      • Hibernate – 1.2 uA
      • Shutdown – 0.1 uA
    • Dimensions – 20 x 16 x 3mm
  • USB – 1x Micro USB port to BL702, 1x Micro USB port for serial console (via CH340 USB to TTL chip)
  • Expansion – 2x 15-pin headers with GPIO, PWN, ADC, UART, I2C, SPI, USB, JTAG, VIN, 3.3V, GND (The headers are soldered based on the descripion)
  • Misc – Enable and Boot buttons
  • Power Supply – 5V via micro USB port, 5 to 6V via VIN pin
XT-ZB1 module block diagram
XT-ZB1 module block diagram


BL702 devkit pinout diagram

English documentation for the module and devkit can be found on bl602.fun website, where we’ll also find a smaller XT-ZB2 BL702 module. Both modules are designed for “serial transparent transmission”, Smart power plugs, Smart LED lights, sensor networks, and industrial wireless control.

Software resources include a link to the bl_mcu_sdk Github repo, an MCU software development kit provided by Bouffalo Lab Team for BL602/BL604, BL702/BL704/BL706, and future RISC-V based chips. There’s also documentation for the SDK, but that part is only in Chinese. The SDK includes samples for BLE and peripherals, but I can’t seem to find any Zigbee or 802.15.4 demos…That’s because that part of the SDK requires an NDA:

BL702 15.4/zigbee SDK is only avaliable (sic.) when NDA is signed

I found about the board through a tweet by Lup Yuen Lee, and Jonathan Beri also commented that the ZigBee stack is usually licensed. So while this BL702 devkit supports Zigbee, an extra license may be required to (legally) use the 802.15.4/Zigbee.

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