Point to Point Communication for RS485-LN
Table of Contents：
- 1. point to point
- 2. Point To Mult-Point
- 3 Point to Point (RS485 Pass Through).
- 4. AT command
- 5. Data Format
1. point to point
1.1 Overview
1.2 Configure
A's configuration: B's configuration:
AT+GROUPMOD=0 AT+GROUPMOD=0
AT+GROUPID=12345678 AT+GROUPID=12345678
AT+TXCHS=868700000 AT+TXCHS=869000000
AT+RXCHS=869000000 AT+RXCHS=868700000
AT+CFGDEV=01 03 00 00 00 04,1 AT+CFGDEV=01 03 00 00 00 02,1
or or
AT+COMMAND=01 03 00 00 00 04,1 AT+COMMAND=01 03 00 00 00 02,1
1.3 Serial port display
A sends a command to B to query B's RS485 sensor data and display it on A's upper computer.
Similarly, B sends a command to A to query A's RS485 sensor data and display it on B's upper computer.
If the sender does not get the ACK reply from the receiver, it will retransmit up to 4 times, each interval is 10 seconds, and the UplinkCounter of the retransmission will not increase. (Retransmission only occurs when using the AT+CFGDEV command or triggering an external interrupt)
2. Point To Mult-Point
2.1 Overview
2.2 Configure
Configuration of the TX group:
AT+GROUPMOD=0,2
AT+GROUPID=12345678
AT+TXCHS=868700000
AT+RXCHS=869000000
AT+CFGDEV=01 03 00 00 00 02,1
or
AT+COMMAND=01 03 00 00 00 02,1
Configuration for RX group number 1:
AT+GROUPMOD=1,1
AT+GROUPID=12345678
AT+TXCHS=869000000
AT+RXCHS=868700000
Configuration for RX group number 2:
AT+GROUPMOD=1,2
AT+GROUPID=12345678
AT+TXCHS=869000000
AT+RXCHS=868700000
2.3 Serial port display
The TX group sends broadcast data to the RX group. After the RX group receives the data, it will reply to the TX group in order from small to large.
If the sender does not get the ACK reply from the receiver, it will retransmit up to 4 times, each interval is 30 seconds, and the UplinkCounter of the retransmission will not increase.(Retransmission only occurs when using the AT+CFGDEV command or triggering an external interrupt)
3 Point to Point (RS485 Pass Through).
3.1 Overview
PC --> RS485 to USB adapter --> RS485-LN A<-----LoRa ----> RS485-LN B<-- >RS485 sensor
3.2 Configure
Configuration of the PC:
RS485 sensor read command
Configuration for RX group number 1:
AT+MOD=1,500
AT+GROUPID=12345678
AT+TXCHS=869000000
AT+RXCHS=868700000
Configuration for RX group number 2:
AT+GROUPID=12345678
AT+TXCHS=869000000
AT+RXCHS=868700000
Configure parameters consistent with the RS485 sensor：
AT+BAUDR=4800
AT+PARITY=0
AT+DATABIT=8
AT+STOPBIT=0
AT+SCHEDULE=0,0
AT+CMDDL=400
3.3 Serial port display
If the sender does not get the ACK reply from the receiver, it will retransmit up to 4 times, each interval is 30 seconds, and the UplinkCounter of the retransmission will not increase.(Retransmission only occurs when using the AT+CFGDEV command or triggering an external interrupt)
4. AT command
ATZ : Trig a reset of the MCU
AT+FDR : Reset Parameters to Factory Default, Keys Reserve
AT+FCU : Get or Set the Frame Counter Uplink
AT+FCD : Get or Set the Frame Counter Downlink
AT+TXP : Get or Set the transmit power, the maximum is 20dBm (default is 14dBm)
AT+SYNC : Get or Set the Sync word [1:0x34,0:0x12] (default is 1)
AT+PMB : Get or Set the preamble (default:8)
AT+TXCHS : Get or Set the transmit frequency of TX (default:868700000)
AT+TXSF : Get or Set the spreading factor of TX (7 to 12) (default:12)
AT+RXCHS : Get or Set the transmit frequency of RX (default:869000000)
AT+RXSF : Get or Set the spreading factor of RX (7 to 12) (default:12)
AT+BW : Get or Set the bandwidth [0:125khz,1:250khz,2:500khz] (default:0)
AT+CR : Get or Set the coding rate [1: 4/5, 2: 4/6, 3: 4/7, 4: 4/8] (default:1)
AT+TDC : Get or set the application data transmission interval in ms(default 10 minutes)
AT+VER : Get firmware version number
AT+SEND : Set Custom sent hex data
AT+GROUPMOD : Set or Get the grouping mode of the device (default: 0)
AT+GROUPID : Set or Get the password for matching between TX group and RX group, which can be composed of numbers or characters (default: 12345678)
AT+INTMOD : Get or Set the trigger interrupt mode
AT+BAUDR : Get or set the baud rate of rs485. (default: 9600)
AT+DATABIT : Get or Set databit(7:7 bits,8:8 bits) of rs485 (default: 8)
AT+PARITY : Get or Set parity(0:none,1:odd,2:even) of rs485(default: 0)
AT+STOPBIT : Get or Set stopbit(0:1 bit,1:1.5 bit,2:2 bit) of rs485(default: 0)
AT+CMDDL : Get or Set the delay waiting time after receiving RS485 command (default: 400)
AT+CRCCHECK : Get or set to receive and verify RS485 sensor data (0: Disable,1:CRC16_MODBUS) (default: 1)
AT+SCHEDULE : Each TDC sends command data to the receiver.
AT+CFGDEV : Instantly send RS485 commands to the receiver.
AT+RS485 : Send commands to the local RS485 device.
AT+MOD : Get or set the host send mode.(default: 0)
Example 1:
AT+SEND=01020304 will send a payload of 01020304
Example 2:
AT+INTMOD=aa (0:Disable,1:falling or rising,2:falling,3:rising) (default: 2)
RS485-LN support external Interrupt uplink since hardware v1.2 release.
Connect the Interrupt pin to RS485-LN INT port and connect the GND pin to V- port. When there is a high voltage (Max 24v) on INT pin. Device will send an lora packet.
Example 3:
AT+SCHEDULE: This command will be sent to Group RX during each transmission, Max command length is 14 bytes. The grammar is:
AT+SCHEDULE =xx xx xx xx xx xx xx xx xx xx xx xx,m
xx xx xx xx xx xx xx xx xx xx xx xx: The RS485 command to be sent
m: 0: no CRC, 1: add CRC-16/MODBUS in the end of this command
For example, if we have a RS485 sensor. The command to get sensor value is: 01 03 0B B8 00 02 46 0A. Where 01 03 0B B8 00 02 is the Modbus command to read the register 0B B8 where stored the sensor value. The 46 0A is the CRC-16/MODBUS which calculate manually.
Example 4:
AT+CFGDEV : This command will be sent to Group RX.
The grammar is:
AT+CFGDEV =xx xx xx xx xx xx xx xx xx xx xx xx,m
xx xx xx xx xx xx xx xx xx xx xx xx: The RS485 command to be sent
m: 0: no CRC, 1: add CRC-16/MODBUS in the end of this command.
Example 5：
AT+RS485: This command will be sent to local RS485 device.
The grammar is:
AT+RS485 =xx xx xx xx xx xx xx xx xx xx xx xx,m
xx xx xx xx xx xx xx xx xx xx xx xx: The RS485 command to be sent
m: 0: no CRC, 1: add CRC-16/MODBUS in the end of this command.
Example 6：
AT+MOD=0 Commands are transparently transmitted through UART.
AT+MOD=1,500 Commands are transparently transmitted through RS485. 500 ms after the first character is received from RS485, all characters are commands.
Example 7：
AT+GROUPMOD=0 Set to point to point mode
AT+GROUPMOD=0,aa Set the TX group that controls the number of aa (The maximum value of aa is 8)
AT+GROUPMOD=1,bb Set to the RX group controlled by the TX group, numbered bb(The maximum value of bb is 8)
AT+GROUPMOD=0,2 Set to control the TX group of the two RX groups
AT+GROUPMOD=1,1 Set the RX group numbered 1
AT+GROUPMOD=1,2 Set the RX group numbered 2
5. Data Format
8 bytes of GROUPID +n payload + 4 bytes of checksum
Payload(S12, SF11, SF10 maximum length is 59, SF9 maximum length is 123, SF8, SF7 maximum length is 230):
| Size (bytes) | 1 | 1 | 1 | 1 | payloadsize |
|---|---|---|---|---|---|
| Value | address | request | ACK | payloadsize | command data or return data |
The first byte： 00 is the broadcast address, 01-08 is the RX group number
The second byte： send request when not 0, not request when it is 0
The third byte： ACK returned to the sender.
The fourth byte： The command length of the sender or the data length of the RS485 sensor returned by the receiver.
The Fifth byte： RS485 command or RS485 return data.