1. Introduction
The OpenThread Border Router (OTBR) is crucial in Matter to enable the communication between IP-based networks. It acts as a bridge between the Thread network and the outside world.
A Thread Border Router supports at least the following functions:
- Bidirectional IP connectivity between Thread and Wi-Fi/Ethernet networks.
- Bidirectional service discovery via mDNS (on a Wi-Fi/Ethernet link).
- Thread-over-infrastructure that merges Thread partitions over IP-based links.
- External Thread commissioning (for example, a mobile phone) to authenticate and join a Thread device to a Thread network.
2. STM32MP1 OpenThread border router
The STM32MP1 OTBR works with the NUCLEO-WB55RG or NUCLEO-WBA55CG radio coprocessor (RCP), which is connected to the STM32MP157F-DK2 Discovery kit (wiki for STM32MP15 Discovery kits) or STM32MP135F-DK Discovery kit (wiki for STM32MP13 Discovery kits) through a serial connection using an FTDI for NUCLEO-WB55RG and USB for NUCLEO-WBA55CG.
| OpenThread Border Router |
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2.1. Required boards
- As OpenThread Border Router:
- As Thread® RCP firmware, NUCLEO-WB55RG or NUCLEO-WBA55CG ST radio coprocessor (RCP):
2.2. STM32MP157F-DK2 and STM32MP135F-DK installation
A Linux® PC running under Ubuntu® 18.04 or 20.04 is required. The developer can follow this link.
The Linux package can be found on Github.
3. NUCLEO-WB55RG RCP installation and hardware connection
3.1. NUCLEO-WB55RG RCP installation
- Step 1: Discover the NUCLEO-WB55RG hardware by following this link.
- Step 2: Get the firmware
- For X-CUBE-MATTER version 1.0 get the X-CUBE-MATTER from st.com.
- For X-CUBE-MATTER version higher than 1.0, the RCP binary is no more included in X-CUBE-MATTER delivery and should be generated using STM32CubeWB version 1.18.
- Step 3: Install the firmware by following this link.
3.2. NUCLEO-WB55RG RCP hardware connection
The communication is done through a serial connection. For RCP implementation, UART Rx/Tx are routed to the CN10 pin 35 (Tx) and the pin 37 (Rx) of an external connector. If the platform host uses USB, a USB/UART converter (e.g. FTDI) is needed. In this case, connect its Rx connector (usually the yellow one) to the CN10 pin 35, and its Tx connector (usually the orange one) to the CN10 pin 37. Black connector (i.e. ground) can be found on the CN10 pin 32.
| STM32WB RCP hardware connection |
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4. NUCLEO-WBA55CG RCP installation and hardware connection
4.1. NUCLEO-WBA55CG RCP installation
For programming the P-NUCLEO-WBA55 platform, generate the RCP binary (not included in any X-CUBE-MATTER delivery) using STM32CubeWBA, and use STM32CubeProgrammer to program the Arm® Cortex® M33 CPU at the start address: 0x0800 0000.
4.2. NUCLEO-WBA55CG RCP hardware connection
The communication is done through a USB serial connection.