Sollae Systems P4M-440G MQTT Client Module User Manual

Sollae Systems P4M-440G MQTT Client Module

Introduction

P4M-440G is an MQTT client module. This module accepts AT commands via the UART port, providing various features for MQTT communication. As a result, users can implement MQTT functionality on their MCU (Microcontroller) or microcomputer using this module.

Features

• Equipped with MQTT client functionality
• Supports simple control through AT commands
• 1 x 10/100Mbit Ethernet port
• 1 x UART port (default 19200 bps)
• Supports TLS v1.2
• Provides storage capability for Root CA and client certificates
• Supports PC connection via USB
• Provides dedicated management program (PHPoC Debugger)

Hardware Specifications

Interface

| UART| 1 x UART Port (3.3V Level) Baudrate: 1200 ~ 115200 bps

Default: 19200 bps, No-Parity, 8-Data bit, 1-Stop bit

Network| 1 x 10/100Mbps Ethernet
USB| USB Device – PC Connection
Temperature| Operation/Storage| -40℃ ~ 85℃
Environment| RoHS Compliant

Dimension

Dimensions(unit: mm) may vary according to a method of measurement.

Layout

P4M-440G interfaces with two 12 x 1 pin headers (P1 ~ P2). The pin spacing is 2mm.

P1

P2

LED
There is an STS LED located at the top-left corner of the module. This LED blinks at a 1-second interval.

P3, P4
P3 and P4 are only for the manufacturer.

Interface

System

Pin

|

Description

---|---

+3.3V

| Input the power supply of 3.3V DC to this pin. Make sure the DC voltage is in the range of 3.15V ~ 3.45V. It is recommended to use a power supply capable of supplying more than 500mA current while a stable output of DC 3.3V for stable

operation of the module.

GND| Connect the ground of your main system to this pin. It is recommended that the ground is as wide as possible to shorten the path of the return signal.

RESET#

| This pin is used to restart the system. If you enter a LOW pulse of 1 millisecond (1ms) or more to this pin, the system will restart. Since this pin is LOW Active, normally it should keep it high state(It is internally pulled up with a 10K ohm

resistor.)

ISP#| ISP# pin is used for initialization. Since this pin is LOW Active, normally it should

keep it high state(It is internally pulled up with a 10K ohm resistor.)

VBAT| Connect the battery to VBAT so that the built-in RTC time information and backup SRAM contents are not erased when power is not applied. Connect this pin to

+3.3V if you do not use any battery. The allowable voltage is DC 1.65V to DC 3.6V.

UART

There are two UARTs, each providing RXD and TXD pins.

• Notice: You can activate only one of the UARTs on P4M-440G. The default port is UART0, and you can refer to the AT commands and MQTT configuration for instructions on how to change it.

Ethernet

P4M-440G provides 10/100Base-TX Ethernet Interface. Note that an RJ45 connector is required to use Ethernet. Refer to a circuit diagram of the Application Circuit Diagram for the connection.

USB Device

This port must be interfaced for product management and configuration. After connecting this port and connecting the product with the PC via a USB cable, you can access the product using the PHPoC Debugger. Either type B USB connector, mini USB, or micro USB connector can be used for this port. Please refer to the application circuit diagram for the connection method.

Notice:
The VBUS pin cannot be used for supplying power to P4M-440G.

Application

This is an application circuit diagram for interfaces of P4M-440G.

Software

PHPoC Debugger
PHPoC Debugger is a software used for the management and configuration of PHPoC products. You need to install this program on your PC to use PHPoC.

• PHPoC Debugger Download Page
• PHPoC Debugger Manual Page

Functions and Features of PHPoC Debugger

• Configuration of P4M-440G
• Monitor resources of P4M-440G
• Upgrade Firmware of P4M-440G
• Upload files from the local PC to P4M-440G
• Download files in P4M-440G to the local PC
• Edit files stored in P4M-440G
• Support MS Windows O/S

Connection with a PC

To access the product via PHPoC Debugger, a connection with a PC is required.

USB Connection

1. Connect the USB device port of P4M-440G to the PC via a USB cable.
2. Run the PHPoC Debugger.
3. Select connected COM PORT and press the connect ( ) button.
4. If the USB is successfully connected, the connect button will be inactivated and the disconnect button ( ) will be activated.

Remote Connection
The remote connection is provided. Please refer to the PHPoC Debugger manual page for details.

Initial Setup and Certificates

• IP Address
  P4M-440G is initially configured to automatically obtain an IP address. Therefore, in a typical network where IP addresses are assigned automatically, there is no need for initial IP address configuration. However, if you need to use a static (fixed) IP address, you should connect the product to a PC and refer to the PHPoC Debugger manual for instructions on setting the IP address.

• Password
  If you set a password for the product, you must enter the password when connecting the product via USB or network. Please refer to the PHPoC Debugger manual page for details.

• Certificates
  If you need to store Root CA certificates and client certificates on the module for the MQTT broker connection, please refer to the Managing Certificates section in the PHPoC Debugger manual to store the certificates on the product.

Firmware Upgrade

Firmware can be updated to introduce new features or fix discovered bugs in the product. If the firmware version on your current product is not the latest, it is advisable to perform an upgrade. Firmware can be upgraded either online through PHPoC Debugger or directly. For detailed instructions on firmware upgrades, please refer to the Firmware Upgrade section in the PHPoC Debugger manual.

Reset

Settings Reset
Settings Reset makes all the settings of your PHPoC products to factory default.

Settings Reset Procedure

1 second)

| Initialization mode| On
2| Input LOW signal again over 5 seconds| Preparing initialization| Rapidly

blinks

3| Check if the STS LED is turned OFF| Initialization ready| Off

4

| Release the LOW input right after the STS is OFF. (※ If you don’t release the button within 2 seconds, the state goes back to

the step 2)

|

Progressing initialization

|

On

5| Rebooting automatically| Initial state| Off

Device Initialization
Device Initialization makes all the settings including the saved password of your PHPoC products to factory default. Furthermore, all files stored in flash memory are deleted as well as a certificate. Therefore, it is highly recommended to back up the files stored in the product’s file system and the certificates before performing device initialization.

• Refer to the Device Initialization page of PHPoC Debugger’s Manual for details.

MQTT Usage
This document serves as a guide on how to use the MQTT functionality of the P4M-440G and does not cover detailed information about the MQTT protocol. For in-depth details about the protocol, please refer to the MQTT standard documentation available on the MQTT website.

File System

To use the MQTT functionality of P4M-440G, the following files are required:

communication via UART

p4x_mqtt_x.x.poc| MQTT PXM – Functionality for MQTT communication
phpoc.ini| General configuration file
pxm.ini| PXM configuration file

These files are stored in the P4M-440G’s file system by default, allowing users to immediately utilize the MQTT functionality.

AT Commands

All MQTT functionalities of the P4M-440G are executed through AT commands. Therefore, users need to be familiar with the usage of AT commands.

Basic Format
AT commands and responses are composed of ASCII strings and are case- insensitive. Every AT command always starts with ‘AT’ and ends with ‘’.

• : Carriage Return, 0x0d

Command-List: General

Command List: MQTT

Command

|

Description

---|---
+MCT| Setting Timeout
+MCCF| Setting Connection Flags
+MCCP| Setting Connection Payload
+MCB| Setting QoS
+MNC| Connecting to a Broker
+MND| Disconnecting from a Broker
+MNG| Reading Messages
+MBT| Setting Topic Buffer
+MBM| Setting Message Buffer
+MBP| PUBLISH
+MBS| SUBSCRIBE
+MBU| UNSUBSCRIBE
+MQNS| Getting Status
+MQNU| Getting the number of unread messages
+MQNR| Getting the size of a received message
+MQC| Getting the client ID
+MCO| Setting the short response mode

Command Responses

Device Connection

1. LAN connection and configuration
   Connect P4M-440G to an internet-enabled network and, if necessary, configure the IP address.

2. UART connection and configuration
   Connect the user’s MCU or microcontroller to P4M-440G’s UART0 port and configure it as follows:

   • 19200 bps, No-parity, 8-data bit, 1-stop bit

3. Ready for AT command input
   Prepare the user’s MCU or microcontroller to input AT commands via P4M-440G’s UART.

Topic and Message Buffer

By storing topics and messages in buffers and accessing them using buffer IDs, you can exchange MQTT messages more efficiently. You can use a total of four buffers (with IDs 0 to 3) for topic buffers and message buffers, respectively.

Setting Topic Buffers: +MBT

• Command Format
  AT+MBT=,””

• An example
  at+mbt=0,”test/test_topic_0″
  OK
  at+mbt=1,”test/test_topic_1″
  OK
  at+mbt=2,”test/test_topic_2″
  OK
  at+mbt=3,”test/test_topic_3″
  OK

Setting Message Buffers: +MBM

• Command Format
  • AT+MBM=,””
• An example
  at+mbm=0, “message 0”
  OK
  at+mbm=1, “message 1”
  OK
  at+mbm=2, “message 2”
  OK
  at+mbm=3, “message 3”
  OK

Timeout

Timeout settings provide five parameters, and the unit of the settings is in seconds.

request

| 2| 3
PINGREQ| Timeout for MQTT PINGREQ packet| 2| 4
Keep-Alive| Timeout for Keep-Alive (PINGREQ intevals)| 30| 5

Timeout Setting: +MCT

Command Format
Each timeout value is listed by separating them with commas, without spaces, to the right of the equal sign in the +MCT command. It is essential to list them in the order of their settings. Each value can be omitted, and if omitted, the previous setting value will be retained. When omitting values, you can omit both the commas and the values on the right side based on the value you want to set. However, for the left items of the setting value, you can omit only the values, excluding the commas.

• AT+MCT=,,,,

Examples

• Setting each timeout value to 4, 2, 2, 2, and 30 seconds
  at+mct=4,2,2,2,30
  OK

• Setting CONNECT timeout to 4 seconds
  at+mct=4
  OK

• Setting PUBLISH timeout to 2 seconds
  at+mct=,2
  OK

• Setting SUBSCRIBE timeout to 2 seconds
  at+mct=,,2
  OK

• Setting PINGREQ timeout to 2 seconds
  at+mct=,,,2
  OK

• Setting Keep-Alive timeout to 30 seconds
  at+mct=,,,,30
  OK

Connections

Connection Flags

Three flags are provided for MQTT connection configuration.

Connection Flag Setting: +MCCF

Command Format
Each timeout value is listed by separating them with commas, without spaces, to the right of the equal sign in the +MCCF command. It is essential to list them in the order of their settings. Each value can be omitted, and if omitted, the previous setting value will be retained. When omitting values, you can omit both the commas and the values on the right side based on the value you want to set. However, for the left items of the setting value, you can omit only the values, excluding the commas.

• AT+MCCF=,,

Examples

• Setting each flag to 1, 0 and 0
  at+mccf=1,0,0
  OK

• Setting Clean Session to 1
  at+mccf=1
  OK

• Setting Will QoS to 0
  at+mccf=,0
  OK

• Setting Will Retain to 0
  at+mccf=,,0
  OK

Connection Payload
Five payload settings are provided for the MQTT connection.

Setting Connection Payload: +MCCP

Command Format
Each timeout value is listed by separating them with commas, without spaces, to the right of the equal sign in the +MCCP command. It is essential to list them in the order of their settings. Each value can be omitted, and if omitted, the previous setting value will be retained. When omitting values, you can omit both the commas and the values on the right side based on the value you want to set. However, for the left items of the setting value, you can omit only the values, excluding the commas.

• AT+MCCP=””,””,””,””,””

Examples

• Setting a Client ID
  at+mccp=”test_client_id”
  OK

• Setting a will message
  at+mccp=, “test/will_topic”,” test will message”
  OK

• Setting a will message (Using a topic buffer and a message buffer)
  at+mbt=0,”test/topic_0″
  OK
  at+mbm=0, “message 0”
  OK
  at+mccp=,0,0
  OK

• Setting a username and a password
  at+mccp=,,,”test_user”,”test_password”
  OK

QoS
Three settings for Quality of Service (QoS) are provided.

Setting QoS: +MCB

Command Format
Each timeout value is listed by separating them with commas, without spaces, to the right of the equal sign in the +MCB command. It is essential to list them in the order of their settings. Each value can be omitted, and if omitted, the previous setting value will be retained. When omitting values, you can omit both the commas and the values on the right side based on the value you want to set. However, for the left items of the setting value, you can omit only the values, excluding the commas.

• AT+MCB=,,

Examples

• Setting all parameters to 0
  at+mcb=0,0,0
  OK

• Setting PUBLISH QoS to 0
  at+mcb=0
  OK

• Setting RETAIN flag to 0
  at+mcb=,0
  OK

• Setting requested QoS to 0
  at+mcb=,,0
  OK

Connecting to Broker
P4M-440G can request a connection to an MQTT broker as an MQTT client.

Connect to a Broker: +MNC

Command Format

• AT+MNC=”<Broker’s hostname / IP address>”
• AT+MNC=”<Broker’s hostname / IP address>”,
• AT+MNC=”<Broker’s hostname / IP address>”,,

In some cases, you can omit the port number or protocol. When omitted, the default values will be used.

Notice:
If you specify the port number as 8883 and do not specify the protocol, “tls” will be used as the protocol instead of the default “tcp”.

• An example
  at+mnc=”203.0.113.0″
  OK

• An example is specifying a port number
  at+mnc=”203.0.113.0″,8883
  OK

• An example: Specifying both a port number and a protocol with a hostname
  at+mnc=”example.com”,8884, “tls”
  OK

Check Connection Status: +MQNS

• Command Format
  AT+MQNS

• Response Code
  Code| Description
  ---|---
  0| Not connected
  1| Hostname lookup is in progress
  2| TCP/TLS connection is in progress
  3| TCP/TLS connected + MQTT connection is in progress
  4| MQTT Connected
  5| MQTT Connected + Wait for a response (PUBACK / SUBACK / UNSUBACK)

• An example
  at+mnc=”203.0.113.0″
  OK
  at+mqns
  +MQNS:4
  OK

Disconnect from a Broker: +MND

• Command Format
  AT+MND

• An example
  at+mqns
  +MQNS:4
  OK
  at+mnd
  OK
  at+mqns
  +MQNS:0
  OK

SUBSCRIBE

P4M-440G, as an MQTT client, can request to subscribe to a specific topic on the MQTT broker or request to unsubscribe from topics it has subscribed to.

SUBSCRIBE Request: +MBS

• Command Format

  • AT+MBS=””
  • AT+MBS=

• An example
  at+mbs=”test/test_topic”
  OK
  at+mqns
  +MQNS:4
  OK

• An example is using a topic buffer
  at+mbt=0,”test/test_topic”
  OK
  at+mbs=0
  OK
  at+mqns
  +MQNS:4
  OK

UNSUBSCRIBE Request: +MBU

• Command Format

  • AT+MBU=””
  • AT+MBU=

• An example
  at+mbu=”test/test_topic”
  OK
  at+mqns
  +MQNS:4
  OK

• An example is using a topic buffer
  at+mbt=0,”test/test_topic”
  OK
  at+mbu=0
  OK
  at+mqns
  +MQNS:4
  OK

PUBLISH

P4M-440G, as an MQTT client, can request to publish messages to an MQTT broker.

PUBLISH Request: +MBP

• Command Format

  • AT+MBP=””,””
  • AT+MBP=””,
  • AT+MBP=,””
  • AT+MBP=,

• An example
  at+mbp=”test/test_topic”, “test message”
  OK
  at+mqns
  +MQNS:4
  OK

• An example is using both a topic buffer and a message buffer
  at+mbt=0,”test/topic_0″
  OK
  at+mbm=0,” test message”
  OK
  at+mbp=0,0
  OK
  at+mqns
  +MQNS:4
  OK

Reading

Reading Messages
If there are messages published to the subscribed topics, those messages will be received and can be read. In the case of multiple received messages, you can only read the last received message.

Reading a Message: +MNG

• Command Format

  • AT+MNG=””
  • AT+MNG=

• An example
  at+mng=”test/test_topic”
  +MNG:12,test message
  OK

• An example: Using a topic buffer
  at+mbt=0,”test/test_topic”
  OK
  at+mng=0
  +MNG:12,test message
  OK

Getting the Number of Unread Messages: +MQNU

Command Format

• AT+MQNU
• AT+MQNU=””
• AT+MQNU=

If you omit the topic or topic buffer ID, it will check all subscribed topics.

• An example
  at+mqnu=”test/test_topic”
  +MQNU:1
  OK

• An example is using a topic buffer
  at+mbt=0,”test/test_topic”
  OK
  at+mqnu=0
  +MQNU:1
  OK

Getting the Size of a Received Message: +MQNR

• Command Format

  • AT+MQNR=””
  • AT+MQNR=

• An example
  at+mqnr=”test/test_topic”
  +MQNU:12
  OK

• An example is using a topic buffer
  at+mbt=0,”test/test_topic”
  OK
  at+mqnr=0
  +MQNU:12
  OK

Reading the Client ID
You can read the client ID of the device.

Reading the Client ID: +MQC

• Command Format
  AT+MQC=”client id”

• An example
  at+mqc=”client id”
  +MQC:USER-SCLI-ENTI-DCHK
  OK

• An example is setting with a client ID
  at+mccp=”user_client_id”
  OK
  at+mqc=”client id”
  +MQC:user_client_id
  OK

Notice:
All devices come with unique client IDs by default. If the user does not specify a client ID, this unique value will be used.

Setting Short Response

You can set short responses for AT commands.

Setting short response: +MCO

• Command Format
  AT+MCO=Values| Description
  ---|---
  0| Disable Short Response (Default)
  1| Enable Short Response
• An example
  at+mco=0
  OK
  at+mqns
  +MQNS:4
  OK
  at+mco=1
  OK
  at+mqns
  +4
  OK

ATC & MQTT Settings
ATC and MQTT environment settings can be changed in the PXM environment file (pxm.ini) in the P4M-440G’s file system.

Parameters

ATC

|

atc_uart_opt

|

UART Option

|

“n81n”

| “n81n”(fixed)

–  n: No parity

–  8: 8 data bits

–  1: 1 stop bit

–  n: No flow-control

ATC| atc_cmd_buf_size| Command Buffer Size

(Byte)

| 256| 128 ~ 2048
MQTT| mqtt_max_topic_len| Max. Topic Buffer Size

(Byte)

| 128| 64 ~ 1024
MQTT| mqtt_max_msg_len| Max. Message Buffer Size

(Byte)

| 256| 64 ~ 4096
MQTT| mqtt_max_pub_buf| MQTT PUBLISH Topic

Buffer Quantity

| 4| 4 ~ 32
MQTT| mqtt_max_sub_buf| MQTT SUBSCRIBE Topic

Buffer Quantity

| 4| 4 ~ 32

Due to limited memory capacity, MQTT buffer-related settings may not be usable even within the specified range depending on the settings of other items. It is recommended to use default values, so please only change them if absolutely necessary, and make sure to conduct sufficient testing after the changes.

Procedures

1. Access the P4M-440G’s file system using PHPoC Debugger.
2. Select the pxm.ini file in the file system.
3. Modify the values of the configuration items.
4. Upload the modified file system.
5. Reboot the device.

Examples

• Changing the UART baud rate to 9600 bps
  pxm.ini (original)| pxm.ini (modified)
  ---|---
  atc_uart_baud=19200| atc_uart_baud=9600
  mqtt_max_topic_len=128| mqtt_max_topic_len=256
  ---|---
• Changing the maximum MQTT topic buffer size to 256 bytes

Caution
If you modify or delete files stored in the P4M-440G’s file system, MQTT functionality may not work correctly. In such cases, you should use PHPoC Debugger to re-upload the ATC/MQTT package to the P4M-440G’s file system. You can download the ATC/MQTT package from the online repository.

Activating PHPoC Engine

P4M-440G is a programmable module, but this feature is initially disabled. To enable user programming on P4M-440G, you need to activate this setting, which can be done in the basic environment file (phpoc.ini) in the P4M-440G’s file system.

Setting Procedures

1. Access P4M-440G’s file system using PHPoC Debugger.
2. In PHPoC Debugger’s file system view, select the phpoc.ini file.
3. Change the “init_php” item in the phpoc.ini file from “Off” to “On” as follows:
   phpoc.ini (original)| phpoc.ini (modified)
   ---|---
   init_php = Off| init_php = On
4. Upload the modified file system.
5. Reboot the device.

Caution

• Enabling the user programming feature provides access to several interfaces and additional functions. However, using too much memory for programming may impact the operation of the MQTT feature. Therefore, it is recommended to enable it only when necessary.
  • For detailed information on P4M-440G with the user programming feature enabled, please refer to the P4M-440G User Manual.
• If you modify or delete files stored in the P4M-440G’s file system, MQTT functionality may not work correctly. In such cases, you should use PHPoC Debugger to re-upload the ATC/MQTT package to the P4M-440G’s file system. You can download the ATC/MQTT package from the online repository.

Advanced AT Commands

You can read or change IP address-related settings for P4M-440G using AT commands.

IP Address-related Settings

These settings are stored in a buffer called “envs.” Therefore, you need to use AT commands related to “envs” to access each item.

Reading an envs item: +ESR
You can use this command to read a specific item from “envs.”

• Command Format
  AT+ESR=””

• An example is reading the IP address
  at+esr=”ipaddr”
  +ESR:203.0.113.0
  OK

Loading the envs: +EBL

• Command Format
  AT+EBL=”envs”

• An example
  at+ebl=”envs”
  OK

Storing the envs: +EBS

• Command Format
  AT+EBS=”envs”,0xa5c3

• An example
  at+ebs=”envs”,0xa5c3
  OK

Modifying an envs item: +EBW

• Command Format

  • AT+EBW=””,””
  • AT+EBW=””,

• An example: Enabling the DHCP
  at+ebl=”envs”
  OK
  at+ebw=”dhcp”,1
  OK
  at+ebs=”envs”,0xa5c3
  OK

• An example: Using a static IP address (203.0.113.0)
  at+ebl=”envs”
  OK
  at+ebw=”dhcp”,0
  OK
  at+ebw=”ipaddr”, “203.0.113.0”
  OK
  at+ebw=”netmask”,”255.255.255.0″
  OK
  at+ebs=”envs”,0xa5c3
  OK

References

• Example Domain
• Releases · phpoc/atc-mqtt · GitHub

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