SDL04 configuration

AT commands

  • ATA: sets the device into online/data mode.

  • ATg or ATG: defines whether interfering RF signals are present. SDL sweeps the operating band and provide a display of mean and peak signal levels, in dBm.

  • ATN: provides a detailed scrutiny of the RF environment. The specific start and stop frequencies, along with step size and dwell time are definable. An ATN command example is ATN 905.250 908.500750 25 100, where:

    • 905.250 is the start frequency in MHz up to 6 decimal digits.

    • 908.500750 is the stop frequency in MHz up to 6 6 decimal digits.

    • 25 is the step increment in kHz, it can be from 1 to 1000.

    • 100 is the dwell time in ms, it can be from 1 to 1000.

  • AT&Fn: where “n” is a number, it establishes a default configuration.

    • AT&F1 FH Master Fast PMP

    • AT&F2 FH Slave Fast PMP

    • AT&F3 FH Repeater Fast PMP

    • AT&F4 FH Master Slow PMP

    • AT&F5 FH Slave Slow PMP

    • AT&F6 FH Master Fast PP

    • AT&F7 FH Slave Fast PP

    • AT&F8 FH Master Slow PP

    • AT&F9 FH Slave Slow PP

    • AT&F10 FH Master Fast PMP no Time ACK

    • AT&F11 FH Master Fast P2P no Time ACK

    • AT&F12 FH Master Fast PP no Time ACK

    • AT&F15 FH Master WL

    • AT&F16 FH Slave WL

    • AT&F18 FH Master Fast TDMA

    • AT&F19 FH Slave Fast TDMA


    • Mesh Primary Coordinator - Each Mesh network must have a primary coordinator. The primary coordinator provides the synchronization for the network.

    • Mesh Secondary Coordinator - Secondary coordinators can be deployed to extend the range of the Mesh network. Each device on a Mesh network must have LOS (Line of Sight) with either a Primary or Secondary Coordinator.

    • Mesh Remote (Slave) - Any device on the network that is not a Primary or Secondary Coordinator, generally attached to end devices. Can also be used to perform routing tasks if enabled.

    • Master (PMP/PP) - Only one per network. In PP/PMP network types (see S133) data either originates at, is destined to, or passes through the Master.

    • Repeater (PMP/PP) - May act simply as a ‘Repeater’ to store and forward data to/from an upstream unit to/from a downstream unit (e.g. when there is a long distance between units), or, may act as a Repeater/Slave in which case the above function is performed AND the unit may also exchange data as a Slave within the network.

    • Slave (PMP/PP) - Interfaces with remote devices and communicates with Master either directly or via Repeater(s).

  • AT&V: displays all visible S registers and their current values.

  • AT&W: writes configuration into non-volatile memory

  • ATSxxx?: displays the xxx register.

  • ATSxxx=yyy: writes value yyy in register xxx.

  • ATSxxx /?: displays the xxx register settings (if they are available).

  • ATIn: where n is one of the following numbers.

    • 1 Product Code.

    • 3 Product Identification (Firmware Version).

    • 4 Firmware Date.

    • 5 Firmware Copyright.

    • 6 Firmware Time.

    • 255 Factory-Configured Options listing.

  • ATlogin: enables a password to access command mode.

  • ATM: provides information about mesh, such as the current routing table, routing logs and errors.

  • ATP0: allows a user to edit the primary frequency table channel by channel. The user can press ESC to exit from editing mode. Any valid frequencies typed will be saved into the table automatically. The BACKSPACE key can be used to correct mistakes when typing a frequency. Once ENTER is pressed, the value will be accepted if it has the right format. An accepted value can NOT be modified with the BACKSPACE key. If changing is desired, the table has to be entered.

  • ATP1: allows a user to edit the secondary frequency table channel by channel. This command is employed like ATP0.

  • ATP0?: shows the primary available frequencies and bandwidth for each channel, as well as the direction of communication allowed on that channel.

  • ATP1?: shows the secondary available frequencies and bandwidth for each channel, similar to ATP0.

AT registers

The most of configurations is defined by registers, which are compound of the letter “S” and a number.

  • S0: selects the mode that the device will haVve when starting up.


    • 0 - command mode

    • 1 - Data mode (default)

  • S2: ascii value for the character that will be used for escape detection.

    • It can be from 0 to 255. 0 disables the scape detection.

    • 43 (character “+”) is the default value.

  • S101: operating mode. Function that SDL will do.

    • 0 - Master. Data originates or passes trhought the master. Only one master can exist in a PP/PMP network.

    • 1 - Repeater. SDL sends data received from RF, it can also exchange data as a slave.

    • 2 - Slave. The device communicates with the master (directly or through repeaters).

  • S102: serial baud rate for serial communications. The data rate must be the same for the serial device connected to SDL. When forcing to Command Mode, the data port will temporarily communicate at the default value.

    Values (bps):

    • 0 - 230400

    • 1 - 115200

    • 2 - 57600

    • 3 - 38400

    • 4 - 28800

    • 5 - 19200

    • 6 - 14400

    • 7 - 9600 (default)

    • 8 - 7200

    • 9 - 4800

    • 10 - 3600

    • 11 - 2400

    • 12 - 1200

    • 13 - 600

    • 14 - 300

  • S103: Wireless Link rate at which RF communications will occur. All radios within a particular network must be configured with the same wireless link rate. Faster link rates sacrifice sensitivity.

    Values (bps):

    • 0 - 172800 (default)

    • 1 - 230400

    • 2 - 276480

    • 3 - 57600

    • 4 - 115200

  • S104: Network address as ID. All modems in a given network must have the same address.

  • S105: Unit address. Unique identifier for each radio in a network. It can be from 1 to 65534.

    • 1 - Address for master.

    • 65535 - Broadcast address.

  • S108: Output power. Trasmission power for the antenna in dBm, it should be as low as possible while the fade margin is appropiate. It can be from 20 to 30.

    • 30 is the default value (equivalent to 1 W).

  • S109 (only for masters with PP or PMP configuration): Hop interval. It defines the rate to change frequency for all radios in the same network. Long intervals have large throughput. Short intervals have low latency and are more reliable to interferences. It can be from 0 to 61, with 20 as default.

  • S110: Data format on the serial port. The value must match with the serial device. When forcing to command mode, SDL will temporarily communicate at the default value. When returning to Data Mode, the configuration will take again the values from S102 and S110.



Stop bits

Data bits

































  • S111: Packet minimum size. This is the minimum number of collected bytes in one buffer, before the buffer can be closed by the character timeout (timer controlled by S116). It can be from 1 to 225, with 1 as default.


    It is STRONGLY advised not to modify this parameter, since changing S111 may prevent the SDL from detecting the escape sequence.

  • S112: Packet maximum size. It defines the number of bytes from the connected device that will be encapsulated into a packet, unless the timer S116 expires. Large packets produce better data throughput; however, small packets are less likely to become corrupted, with less impact in that case. It can be from 1 to 256, with 256 as default.

  • S113: This register determines the maximum number of times that a packet will be retransmitted (in addition to the initial transmission). Retransmissions provide system robustness and ensure data delivery. Retransmissions create additional traffic. It can be from 0 to 254, with 254 as default.

  • S115 (with mesh configuration): Repeat interval. It defines the difficulty to access the RF channel. The bigger the number, less attempts are required to access, but the latency will be larger. It can be from 0 to 255, with 5 as default.

  • S115 (with PP or PMP configuration): Repeat interval. It defines the number of slots which are available within a window of opportunity for remote units to submit channel requests to the Master. Remotes will randomly contend for the ability to access the channel request slots. For a small number of Remotes, it is advisable to keep S115 closer to the default value so as to not ‘waste bandwidth’ by maintaining a relatively large window housing a greater-than-necessary number of channel reservation request slots. It can be from 0 to 255, with 3 as default.

  • S116: Character Timeout in quarters of character time. It can be from 10 to 255, with 10 as default (2.5 character time). Radio Link will accumulate data in buffers from the serial port, until one of the following conditions occur:

    • The Maximum Packet Size (S112) has been accumulated.

    • Minimum Packet Size (S111) has been accumulated AND the Character timeout (S116) has expired.

    After that, the message is sent through RF.

  • S118 (with PP or PMP configuration): synchronization with master or repeater. The default value is 1.


    • 65535: SDL will synchronize with an upstream unit which has the same network address (S104). If that upstream unit fails, it will attempt to synchronize with another upstream.

    • From 1 to 65534: specific address to synchronize.

  • S119: Quick Enter to Command Mode.


    • 1 - Enabled. A delay of 5 seconds is introduced at powerup before the modem will go into data mode. If during these 5 seconds, the user enters ‘mhx’ the modem will instead go into Command Mode and reply with ‘OK’. The terminal baud rate must be set to 9600bps. If an incorrect character is entered, the modem will immediately go into data mode.

    • 0 (default) - The radio will promptly go into data mode upon power-up.

  • S123: average signal strength received over the previous 8 hop intervals, from -110 to -55 dBm.

  • S124: average signal strength received over the previous 8 hop intervals from a slave or repeater. It can be from -110 to -55 dBm.


    The “ATS124 /?” command will show the RSSI statistics (minimum, maximum, average, channel and frequency).

  • S130: synchronization intake. It defines if the modem will accept data when/if the remote has become unsynchronized from the master.


    • 1 - Enabled. The modem will accept data and buffer it until the unit is synchronized.

    • 0 - Disabled (default). Any data received will be ignored.

  • S133: Network Type. This register must be set to the same value on every unit in the RF system.


    • 0 - Point to Multipoint (PMP).

    • 1 - Point to Point (PP).

    • 2 - Peer to Peer or Everyone to Everyone.

    • 3 - Reserved.

    • 4 - PMP with acks.


    • Point to Multipoint - The Master broadcasts data to all units, and all remote units send data back to the Master.

    • Point to Point - Point to point traffic between a master and a slave (with 0 or more Repeaters in between).

    • Peer to Peer - involves either communication between 2 (typically remote) units (P2P) or between all units (Everyone-2-Everyone - E2E).

  • S139: Compatible_21 at 345.


    • 1 - Enabled: SDL will be compatible with the MHX2421 operating at a link rate of 345kbps.

    • 0 (default) - Disabled.

  • S140: Destination address. Ultimate destination for a radio.

    In PP or PMP, the value can be from 1 to 65535, where 65535 is broadcast.

    • PMP - Master S140=65535 and remote S140=1.

    • PTP - Master S140=UA of remote, remote S140=1 (Master).

    • P2P - Master S140=65535, S140 of each (of 2 / pair) remote modem is the UA of the other.

    • E2E - S140 of all modems=65535 (broadcast).

  • S141 (for master): registers the presence of repeaters in the network.

    • 0 - No repeater

    • 1 - 1 or more repeaters.


    with one or more repeaters in the system, a networks throughput is divided in half.

  • S142: Serial channel mode for the data port.

    • 0 - RS-232 (default)

    • 1 - RS-485 half duplex

    • 2 - RS-485 full duplex


    The radio module of SDL is able to transmit through RS-485, but SDL itself is not built to operate with RS-485. The register S142 must not be changed and keep as 0.

  • S150 (only for master radio): it dictates which synchronitation mode will be used when it initially goes online. Quick synchronization mode results in the master hopping very quickly, which will enable a downstream unit to become synchronized faster.


    • 0 - Normal synchronitation.

    • 1 - (Only for PTP configuration). The Master will stay in quick synchronization mode until such time as it receives an acknowledgement from its associated slave, it will then remain hopping quickly for the number of hop intervals (8-255) defined by S152 (Fast Sync Hold on Ack), after which time it will go into normal sync mode.

    • 2 - The master will go into quick synchronization mode when it initially comes online, then it will remain in that mode for the time specified in S151 and finally return to normal synchronization mode.

  • S151: This register settings applies only to a Master modem. Effective only when S150=2. It defines how long, a master modem will stay in fast synchronization mode after it initially goes online.

    Values in ms: from 100 to 6500, with 200 as default.

  • S153: address tag. If this register is enabled with 1, the radio prepends 4 extra bytes to the data (in the same order):

    • First byte =0x00.

    • Second = 0xFF.

    • Third = source unit address (high byte) .

    • Fourth = source unit address (low byte).

    By default, this register is set as 0 - disable.

  • S158: FEC method. FEC consumes significant bandwidth: depending on which coding rate is chosen, a number of coding bits are transmitted along with the data bits. In noisy or long-range communications environments, FEC may effectively increase throughput by decreasing the amount of packet retransmissions which would otherwise be required. FEC may extend RF communications range: at a certain distance where data would otherwise be unacceptably corrupted, employing FEC may be all that is required to maintain the integrity of that data at that distance.




    Information rate

    Number of corrected bits


    No FEC






    1 out of 7


    Hamming (15,11)


    1 out of 15


    Hamming (31,24)


    1 out of 31


    Binary BCH (47,36)


    2 bits


    Golay (23, 12, 7)


    3 bits


    Reed-Solomon (15,11)


    2 nibbles

  • S163: it enables CRC checking of received data on local diagnostic port. Note that even if disabled, the incoming data must have two dummy bytes transmitted in place of crc bytes.

    • 0 - Disable.

    • 1 - Enable (default).


    Disabling CRC check is only advisable during troubleshooting of the user’s diagnostic requests.

  • S167: Tx enable. Enables RF emission.


    • 0 - Disable. The radio will never transmit data, it will be in a listen only mode.

    • 1 - Enable (default). The radio will be able to send data.

  • S213: packet retry limit. Valid only from child to parent.

    Values: from 0 to 254, with 5 as default.

  • S214: number of retransmission of diagnostic packets.

    Values: from 0 to 254, with 0 as default.

  • S215 (with mesh configuration): defines the number of synchronization slots available in a Mesh Frame. In systems with many coordinators, additional slots may be required to avoid collisions. Register S216 can also be used to provide randomness in sending sync packets to avoid collisions. S215 must be set to the same value for each modem on the network or the unit will not synchronize. The value can be from 1 to 10, with 1 as default.

  • S216 (with mesh configuration): defines how often the coordinator transmits synchronization packets. After each synchronization packet transmission the coordinator picks a random number from 1 to the value in S216 and transmits the next packet in this slot. 1 - every synchronization slot, 2 — on average once every 1.5 slots, 3 - on average once every 2 slots etc.

  • S217: Protocol type. Defines how data is sent as output on the local serial port. When Modbus RTU is enabled, there is a delay between the packets coming out of the serial port. The register S146 defines the delay between individual packets.


    • 0 - Transparent Serial (default)

    • 1 - Modbus RTU

  • S218 (with mesh configuration): Input framing type. Controls how the radio treats data coming to serial port. It allows the destination address to be embedded into the data stream, which is automatically stripped by the SDL before transmitting the packet.


    • 0 - Transparent Serial (Default)

    • 1 - Destination Address (DA) is in the first six bytes (high byte first) of the packet. The radio strips these six bytes and doesn’t transmit them. For example, if the DA is 01:23:45:67:89:AB then the high byte is 0x01,the lowest byte is 0xAB. Note that the max size of the data itself in this case is S112 minus 6. If S112 = 256 then the max data size is 250 bytes.

  • S217: protocol type.


    • 0 (default)- Transparent operation. For most applications this value will be maintained in this register.

    • 1 - MODBUS operation. The radio will frame the output data to comply with MODBUS specifications.

    • 2 - DF1 filtering. In this mode, the PLC’s address must match the unit address of the modem. Data not intended for a specific PLC/Modem pairing will be blocked from passing through the modem to the attached PLC.

  • S238: Hopping mode register, preset by manufacturer. It is a readonly register for the end user. S238 controls the modem either hopping on pattern or on frequency table.


    • 0 - Hopping on pattern.

    • 1 - Hopping on frequency table.

    • 2 - Hopping on channel.

    • 3 - Hopping on frequency.

  • S244: channel request mode.


    • 0 (default) - Channel request. It allows a Remote modem which has data to send to request from the Master permission to do so. When granted, the Remote will be allowed to transmit all of its data (no other Remotes may transmit during this period), upon completion of which it will release the channel. This feature eliminates collisions which would otherwise occur if a number of Remotes were all trying to transmit at the same time.

    • 1 - TDMA mode. It relates to channel requests where, in TDMA mode, the Master does not allow such requests from remotes; the master sequences through a list of remotes, giving each one in turn an opportunity to transmit.

  • S248: synchronitation timeout. This register defines how many hop intervals where the slave does not receive a synchronization packet from the master, before it will become unsynchronized and begins to search for a master.

    Values: from 1 to 65534, with 512 as default.

  • S251: in TDMA mode (see S244) this register determines how long, in hop intervals, the Master will wait for a Remote to either (a) begin to send data or (b) indicate that it has completed sending all of its data, prior to the Master sequencing to the next Remote to be given permission to transmit.

    Values (in hops): from 1 to 254, with 10 as default.