The UART interface is designed to send text or hex commands between an external device (e.g., Arduino) and a host. The maximum command or data block size is 127 bytes. Every command line may terminate with a special configurable byte (Packet end): CR (0x0D), LF (0x0A), 0x03 (ETX), or any user-defined value in the Byte field. The firmware also adds the ending signature to each of the commands that the device receives from a host and outputs to UART. If the end signature is not defined, the firmware waits 300 ms and outputs the whole buffer to a host.

The firmware supports only one UART interface, even if a chip has more UART interfaces.

Communication parameters

Baud rate: you can select it in the configuration
Data bits: 8
Parity: None
Stop bits: 1

CC2530

UART uses fixed pin:
P02 – RX (receive).
P03 – TX (transmit).
All pins have the TTL level 3.3V.

You should enable UART on P02 on an output pin in the configuration. Pin P03 is optional.

CC2652

This chip allows using UART on any unused pin. All pins have the TTL level 3.3V.

• You should define the RX pin first.
• If you define only one pin in the configuration, the firmware supposes that it is the RX pin, and the firmware calculates the TX pin number automatically as TX = RX + 1
• If you define two UART pins, you can use any pin number, but the RX pin is always first.

The figure below shows an example with RX and TX pins: P12 – RX, P14 – TX.

FYI: TI LaunchPad™ kit with CC2652R uses P02 and P03 for RX and TX accordingly for XDS110 User UART.

Zigbee clusters

Zigbee cluster: ZCL_CLUSTER_ID_GEN_MULTISTATE_VALUE_BASIC
Zigbee attributes: ATTRID_IOV_BASIC_STATE_TEXT - UART data. You should use the "ZCL_DATATYPE_OCTET_STR" (0x41) or "ZCL_DATATYPE_CHAR_STR" (0x42) data types for this attribute.

Zigbee2MQTT commands

write – sends data to a UART.

Topic: zigbee2mqtt/[friedly_name]/set/action
Payload: text command

The following command allows you to send any bytes. The first byte in the array (2) is the number of bytes following the length.

Topic: zigbee2mqtt/[friedly_name]/set
Payload: {"action": [2, 0, 0]}

Example

if you want to send the following sequence of bytes: 0xAA 0x03 0x08 0x10 0x04 0xC9.

1. Convert all bytes to decimal: 170 3 8 16 4 201.
2. Count your bytes: 6.
3. Make a payload string: {“action”: [6, 170, 3, 8, 16, 4, 201]}
4. Send it using MQTT Explorer or a similar utility:
   1. Select the device in the tree (fig. 1).
   2. Go to “Publish” and specify the full topic name.
   3. Specify the payload.
   4. Click the Publish button.

The figure below shows data received from CC2530 on a Windows-based computer using Advanced Serial Port Monitor. Moreover, you can send data back using this terminal program by typing the necessary bytes in the edit box: AA#03#08#10#04#C9. Here, you do not need to count bytes and add the number in the front.