This is an implementation of an MQTT Battery Monitor. Allows a 12V battery to be monitored via WIFI. Code is compiled using the toolchain referenced below.
Features:
- Monitor Voltage, Current (charge and discharge), and Power
- Programmable shunt current and voltage.
Hardware Project
A schematic and printed circuit board design for this firmware is located in here
Device Path
The device path encompasses subtopics command and status. Commands are sent to $devicepath/command (which the nodes subscribes to.) All status messages are published by the node on $devicepath/status except for the node configuration which is published on /node/info. The device path is set using the patching procedure described later.
Control Messages
Control messages are received by all nodes on /node/control. These are meant to be used to interrogate the nodes connected to the network, and perform other system-wide control functions.
One control message is currently supported: muster. This directs the node to re-send the node configuration information to /node/info. See the power on message below for further details
Command Messages
Command messages are sent using JSON encoding as follows:
{"command":"command from table below"} For commands without a parameter
{"command":"$COMMAND","param","$PARAM"} For commands with a parameter
Because of limitations with the Espressif JSON parser library, all numbers should be sent as text fields (i.e. quoted)
MQTT commands supported:
| Command | Description |
|---|---|
| query | Returns voltage, current and power in a JSON encoded string |
| shuntamps | Get or set shunt full scale amps |
| shuntmv | Get or set shunnt full scale millivolts |
| survey | Returns WIFI survey information as seen by the node |
| ssid | Query or set SSID |
| restart | Restart system |
| wifipass | Query or set WIFI Password |
| mqttdevpath | Query or set MQTT device path |
Notes:
- $ indicates a variable. e.g.: $COMMAND would be one of the commands in the table above.
- Sending an ssid, or wifi command without "parameter":"$PARAM" will return the current value.
- shuntamps, shuntmv, ssid, wifipass, mqttdevpath change not effective until next system restart
Power on Message
After booting, the node posts a JSON encoded "muster" message to /node/info with the following data:
| Field | Description |
|---|---|
| connstate | Connection state (online) |
| device | A device path (e.g. /home/lab/battmon) |
| ip4 | The IP address assigned to the node |
| schema | A schema name of hwstar_relaynode (vendor_product) |
| ssid | SSID utilized |
The schema may be used to design a database of supported commands for each device.
Here is an example:
{"muster":{"connstate":"online","device":"/home/lab/battmon","ip4":"$IP","schema":"hwstar_battmon","ssid":"$SSID"}}
Last Will and Testament
The following will be published to /node/info if the node is not heard from by the MQTT broker:
{"muster":{"connstate":"offline","device":"$DEVICE"}}
Where $DEVICE is the configured device path
Configuration Patcher
WIFI and MQTT Configuration can optionally not be stored in the source files. It can be patched in using a custom Python utility which is available on my github account as a separate project:
https://github.com/hwstar/ESP8266-MQTT-config-patcher
Post patching allows the configuration to be changed without having sensitive information in the source files.
NB:Post-patching is optional. You can just edit the user_main.c source file and hardcode the configuration.
Toolchain
Requires the ESP8266 toolchain be installed on the Linux system per the instructions available here:
https://github.com/pfalcon/esp-open-sdk
Toolchain should be installed in the /opt directory. Other directories will require Makefile modifications.
NB:Current Makefile supports Linux build hosts only at this time. If someone wants to submit a working Makefile for Windows, I'd be happy to add it to the repository.
LICENSE - "MIT License"
Copyright (c) 2015 Stephen Rodgers Copyright (c) 2014-2015 Tuan PM, https://twitter.com/TuanPMT
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.