Y201-L Technical Manual

Y201-L Specification

Contents

1. Overview
   • Hardware Wiring
   • Working Principle
2. Default Settings
3. Serial Modes and Packetization
4. LoRa Parameters and Communication Modes
5. AT Command Conventions
6. Common AT Commands
7. Typical Configuration Flow
   • Modbus RTU Communication Check
8. Maintenance and Upgrade
9. Troubleshooting

1. Overview

This manual explains configuration, commissioning, maintenance, and troubleshooting for the Y201-L mini LoRa DTU. It covers the serial AT command set, transparent and command modes, LoRa communication modes, relay networking, firmware upgrade, and parameter recovery.

Item	Description
Frequency Band	410 to 493 MHz
Serial Interface	Single-port RS232, RS485, or 3.3 V TTL, depending on the ordered variant
Communication Distance	Up to 5 km
Working Modes	Broadcast, fixed-point, master-slave, relay networking
Configuration Method	Serial AT commands

1.1 Hardware Wiring

Power off before wiring. Select the ordered serial interface and use the terminal labels on the supplied module. The drawings show electrical connections, not connector pin order.

Module power: 9-36 VDC. Connect supply positive to + and negative to -.

RS485 variant: A to A, B to B, signal GND to GND. TX/A and RX/B are the shared terminal labels. Use a twisted pair and terminate only the two physical bus ends when required.

RS232 / TTL variant: cross TX and RX; connect GND to GND. Match the adapter's electrical interface and verify the TTL logic voltage before connecting.

See the Y201 User Manual for model-specific power and uplink connections.

1.2 Working Principle

Two RS485 Y201-L units provide a bidirectional LoRa link between a Modbus RTU master and a field device.

The PLC or data logger sends a Modbus request through the host-side Y201-L. The field-side Y201-L delivers it to the RS485 device, then carries the response back to the host. The DTUs forward serial data; the host controls polling and uses the field device's slave address and register map.

For pulse-counting I/O, the counter remains in the I/O module. The host reads that counter over the wireless link. Use transparent serial mode and LoRa broadcast mode (BRD) for this example; FP and MS modes require the additional framing described in Section 4.

2. Default Settings

Parameter	Default
Serial Baud Rate	9600 bps
Data Bits	8
Stop Bits	1
Parity	NONE
Serial Mode	Transparent mode
Hardware Flow Control	NFC
Base Frequency	410 MHz
Step	1 MHz
Channel	20
Speed Level	5
LoRa Mode	Broadcast mode, BRD
Retransmission Count	0
Retransmission Interval	1000 ms
Relay	OFF
Relay Group ID	0
Relay Rule	0,0

3. Serial Modes and Packetization

3.1 Serial Modes

Y201-L supports two serial working modes:

• Transparent Mode, default: Serial data is packetized and forwarded through LoRa
• AT Command Mode: Serial input is treated as AT commands and downlink data is not transparently forwarded

3.2 Entering AT Command Mode

Recommended sequence:

1. Send +++.
2. Wait longer than the packet interval and less than 3 s; 500 ms is recommended.
3. Send a.
4. Enter AT mode only after receiving +ok.

Notes:

• The device pauses data output for about 3 s after receiving +++
• Send AT queries and settings only after +ok is returned
• AT mode is not saved across power cycles; the device returns to transparent mode after reboot

3.3 Exiting AT Mode

• Send AT+EXIT\r\n and wait for OK.
• Or reboot the device directly

3.4 Packetization

Serial data is transmitted when either condition is met:

• Length trigger: data length >= packet length, default 252, range 5 to 252
• Interval trigger: inter-character gap >= packet interval, default 5 ms, range 0 to 300 ms

4. LoRa Parameters and Communication Modes

4.1 Key Parameters

Parameter	Meaning	Default
Base Frequency, base	Frequency calculation baseline	410 MHz
Step, step	Frequency interval between adjacent channels	1 MHz
Channel, ch	Working channel number	20
Speed, sp	LoRa speed level, 1 to 9; higher speed shortens the relative transmission distance	5
Key, key	LoRa encryption string, 1 to 16 characters; write-only	No default
Device Address, id	Local address in fixed-point or master-slave mode, 0 to 65535	No default

Frequency formula: F = base + step x ch.

The configuration tool displays the base frequency and step in 100 kHz units. For example, 4100 represents 410.0 MHz, and 10 represents a 1 MHz step.

4.2 Broadcast Mode, BRD

• Data is broadcast only and not modified
• Both ends must use the same base frequency, step, channel, and speed
• No extra protocol framing is required

4.3 Fixed-Point Mode, FP

Transmit frame format in hex:

[Target Address(2B)][Target Channel(1B)][Data(nB)][XOR(1B)]

Examples:

• Send to address 0x0001, channel 0x03, data 01 02 03: 00 01 03 01 02 03 02
• Use target address 0xFFFF in fixed-point mode for broadcast transmission

4.4 Master-Slave Mode, MS

• The master must frame data according to the master-slave protocol
• The slave returns uplink data transparently
• Configure the retransmission interval and count to reduce packet loss

Master transmit frame format:

[Target Address(2B)][Data(nB)]

4.5 Relay Networking

Relay networking works with broadcast, fixed-point, and master-slave modes.

Key parameters:

• AT+RELAY: relay enable
• AT+GROUPID: relay group ID
• AT+RELAYRULE: relay input and output rules

Typical rules:

• The sender group ID must match the input rule of the first relay
• The input rule of each relay must match the output rule of the previous relay
• The receiver group ID must match the output rule of the last relay

Contact YenGear to confirm the relay-rule settings for your deployment.

5. AT Command Conventions

5.1 Command Format

• Commands start with AT+ and end with \r or \n
• Commands are case-insensitive, uppercase is recommended
• Maximum command length is 256 bytes, 252 bytes recommended
• Multiple parameters are separated by commas
• Wait for the previous response before sending the next command, maximum timeout about 12 s

5.2 Call Types

Type	Send Format	Return Format
Query	AT+CMD or AT+CMD?	+CMD:value followed by OK
Set	AT+CMD=value1,value2...	OK
Help	AT+CMD=?	+CMD:(range...) followed by OK

5.3 Common Error Codes

Error Code	Meaning
ARGS	Invalid parameter, length, format, or range
ARGC	Invalid number of parameters
CMD_UNKNOWN	Unknown command
CMD_FORMAT	Invalid command format
CMD_LENGTH	Command too long
UN_VIEW	Write-only parameter
DEV_MEMORY	Memory error
DEV_SAVE	Parameter save failed

6. Common AT Commands

6.1 Device and System

Command	Function	Notes
AT+LIST	List supported commands	Use to list commands
AT+VER	Query firmware version	Returns version string
AT+DEVINFO	Query device information	Model, version, SN, and more
AT+ECHO	Enable or disable command echo	ON / OFF; default OFF
AT+BOOTINFO	Set or query boot information	1 to 16 bytes; default Start
AT+REBOOT	Reboot device	Parameters take effect in the current runtime area
AT+EXIT	Exit AT mode	Returns to transparent mode
AT+RSTCFG	Restore backup parameters and reboot	Equivalent to Reload
AT+BKCFG	Back up current parameters	Recommended after commissioning
AT+CLRCFG	Restore factory parameters and reboot	Full factory reset

6.2 Serial Parameters

Command	Parameter	Range / Default
AT+UART1=<baud>,<data>,<stop>,<parity>	Serial settings	baud 1200 to 460800, default 9600; data 7/8, default 8; stop 1/2, default 1; parity NONE/EVEN/ODD, default NONE
AT+UARTTL1=<tm>,<len>	Packet interval and length	tm 0 to 300 ms, default 5; len 5 to 252, default 252

6.3 Basic LoRa Parameters

Command	Parameter	Range / Default
AT+SPEED=<sp>	LoRa speed level	1 to 9, default 5
AT+KEY=<key>	LoRa encryption string	1 to 16 characters, write-only
AT+FREQ=<base>,<step>	Base frequency and step	Example 4100,10, see note below
AT+CH=<ch>	Channel number	Determines frequency with base and step
AT+WMODE=<mode>	LoRa mode	BRD / FP / MS
AT+ADDR=<id>	Local device address	0 to 65535

Note: The configuration tool displays the base frequency and step in 100 kHz units. Use 4100,10 for a 410.0 MHz base and a 1 MHz step.

6.4 Master-Slave and Relay Parameters

Command	Parameter	Default
AT+TMODE=<mode>	MASTER or SLAVE	Depends on device role
AT+RETRANS=<time>,<count>	Retransmission interval in ms and retransmission count	1000,0
AT+RELAY=<state>	ON / OFF	OFF
AT+GROUPID=<id>	Relay group ID, 0 to 255	0
AT+RELAYRULE=<rule1>,<rule2>	Relay input and output rules, 0 to 255	0,0

Contact YenGear to confirm the relay-rule settings for your deployment.

7. Typical Configuration Flow

7.1 Quick Broadcast Configuration

1. Enter AT mode, +++ -> delay -> a -> +ok.
2. Configure both devices with matching wireless parameters:

AT+FREQ=4100,10
AT+CH=20
AT+SPEED=5
AT+WMODE=BRD

3. Set serial parameters if required:

AT+UART1=9600,8,1,NONE
AT+UARTTL1=5,252

4. Back up the current configuration for later recovery:

AT+BKCFG

Parameter changes are saved to the runtime parameter area automatically. AT+BKCFG creates a separate backup used by AT+RSTCFG and Reload.

5. Reboot and verify the link:

AT+REBOOT

7.2 Fixed-Point Mode Configuration

1. Set both ends to the same base frequency, step, and speed:

AT+FREQ=4100,10
AT+SPEED=5

2. Set device addresses:

AT+ADDR=1
AT+ADDR=2

3. Switch to fixed-point mode:

AT+WMODE=FP

4. Send data using the fixed-point frame format.

7.3 Master-Slave Mode Configuration

1. Match the base frequency, step, channel, and speed on both devices.
2. On the master, set AT+WMODE=MS and AT+TMODE=MASTER.
3. On the slave, set AT+WMODE=MS and AT+TMODE=SLAVE.
4. Set retransmission strategy if needed:

AT+RETRANS=1000,0

5. The master sends framed master-slave messages and the slave returns data transparently.

7.4 Relay Networking Suggestions

1. Complete the base communication mode configuration first, broadcast, fixed-point, or master-slave.
2. Enable relay on each node with AT+RELAY=ON.
3. Build the group ID and relay rule chain:

• Sender group ID = first relay input rule
• First relay output rule = second relay input rule
• Receiver group ID = last relay output rule

4. After validating the multi-hop link, run AT+BKCFG to save.

7.5 Modbus RTU Communication Check

1. Read a known register from the field device over a direct wired connection first. Record the serial settings, slave address, function code, starting address, and register count.
2. With power off, fit the LoRa antennas and connect one RS485 Y201-L to the field device and the other to the host. Follow the power and RS485 wiring in Section 1.1.
3. Configure the pair using Section 7.1. Match each DTU's serial settings to its connected device, and match the LoRa base frequency, step, channel, speed, and encryption key if configured. Reboot both DTUs to apply the settings and return to transparent serial mode.
4. Send the same Modbus request from the host. Allow for radio transfer and packetization delays in the response timeout. Start with one request at a time and wait for its response or timeout before sending another.
5. Check the TX/RX indicators and compare the returned register data with the field device's expected value. For a pulse counter, generate a known number of pulses and verify the corresponding count change.

8. Maintenance and Upgrade

8.1 Parameter Partitions

The device uses three parameter areas:

• Runtime Area: Current running configuration, query and set commands act on this area
• Backup Area: Saved by AT+BKCFG
• Factory Area: Factory-fixed default parameters

New parameter values are saved to the runtime area automatically and take effect after reboot. AT+BKCFG copies the current runtime values to the backup area.

Recommended workflow:

1. Finish parameter commissioning.
2. Run AT+BKCFG to create a backup.
3. Use AT+RSTCFG when rollback is needed.
4. Use AT+CLRCFG for a full factory reset.

8.2 Firmware Upgrade

Upgrade steps:

1. Power off the device.
2. Hold the Reload button while powering on and release it after about 3 s to enter upgrade mode.
3. Select the firmware file in the configuration tool and start the upgrade.

Firmware upgrade usually keeps saved parameters. Back up parameters first as a precaution.

9. Troubleshooting

Symptom	Possible Cause	Recommended Action
Cannot enter AT mode	The timing is incorrect or +ok was not received	Retry with +++ -> 500 ms delay -> a
Command returns CMD_FORMAT	The command does not start with AT+ or has no line ending	Check command format and serial line ending
Command returns ARGS/ARGC	Wrong parameter value or parameter count	Run AT+CMD=? to view the valid range
LoRa link does not work	Frequency, step, channel, or speed does not match	Check FREQ / CH / SPEED on both ends
Modbus works over a cable but times out over LoRa	The host timeout is too short, a DTU is still in AT mode, or serial/radio settings differ	Follow Section 7.5; check transparent mode and settings, then allow more time for the response
Radio indicators flash but Modbus data is invalid	Incorrect slave address, function, register range, or additional FP / MS framing	Repeat the known wired request in BRD mode and check the field device's register map
Fixed-point communication fails	Wrong target address or wrong frame format	Check ADDR and the fixed-point frame format with XOR
Packet loss in master-slave mode	Retransmission is not configured or the link is noisy	Increase RETRANS interval and adjust count
Relay link breaks	Group ID and rule chain do not match	Check GROUPID and RELAYRULE across all hops
Parameters revert after Reload or AT+RSTCFG	The desired values were not saved to the backup area	Run AT+BKCFG after commissioning

Quick LED reference:

• Power steady on: power is normal
• WORK regular blinking: module is running normally
• TX flashes once: LoRa packet transmission
• RX flashes once: LoRa packet reception

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• Manufacturer: Hunan YenGear Tech Co., Ltd.
• Address: Room 21014, Building 1, Fudi Xingguang Tiandi, Yingxin Road, Yuhua District, Changsha, Hunan, China
• Email: hi@yengear.com
• Website: www.yengear.com