pimvanpelt / pdu

Mongoose OS metered PDU

Modbus PDU

This is a simple firmware that connects over serial to a 16 channel Modbus current sensor like this one (search for "Multi-channel 16-channel AC current frequency measurement acquisition module RS485 sensor transmitter MODBUS-RTU" on Aliexpress for good examples).

The ESP32 connects using serial to the serial output of the current sensor, before it is turned into RS-485. It is then no longer advised to use RS-485. It will read the current sensor outputs once every 5 seconds, and integrate the total power use per channel. It will periodically save its state to flash (see configuration parameter pdu.state_interval), in order to survive power failures, reboots and firmware updates. When rebooting or updating firmware, case should be taken to persist the state to flash, by calling RPC State.Write (details below).

Prometheus Metrics

TODO(pim) --

The firmware exposes all channel information using the Prometheus exposition format, ready for scraping and integration into a network monitoring system. It also exports several modbus statistics (notably number of reads, number of responses, and number of invalid responses).

API

The firmware exposes several getters over Mongoose OS RPC subsystem. See RPC.List to enumerate them all, and RPC.Describe '{"name": ... }' to show the call proto.

The State RPC Service either writes the statefile describing the current PDU state to flash, or reads it back from flash into memory.

The Channel RPC Service takes either no arguments, in which case report for all channels is given as a list, or if a parameter idx is present, only that one channel is returned as a scalar. Note that channels are run from 0..15. When calling Channel.Clear, which zeros the current and consumption counters, care should be taken to also persist the state to flash with State.Write, so that restarts do not inadvertently restore old state.

Examples:

$ mos call Channel.GetCurrent '{"idx": 13 }'
{ "retval": true, "idx": 13, "current": 0.22 }

$ mos call Channel.GetkWh
{ "retval": true, "kwh": [ 14.51, 0.00, 0.00, 0.00, 0.00, 7.23,
  0.04, 1910.34, 0.00, 0.00, 0.00, 0.35, 4.62, 4.77, 0.00, 0.00 ] }

$ mos call mos call State.Write
{ "retval": true }

$ mos call Channel.Clear '{"idx": 15 }' && mos call State.Write
{ "retval": true }
{ "retval": true }

PubSub

The firmware sends periodical status updates to a configured MQTT server. The following events are sent:

• Startup: A message is sent to /mongoose/broadcast/stat/id with information about the microcontroller and firmware.
• Periodical: A message is sent to ${device_id}/stat/pdu with information about the channels in JSON format.

Examples:

/mongoose/broadcast/stat/id {"deviceid": "esp32_5866D0", "macaddress": "D8A01D5866D0",
                             "sta_ip": "192.168.2.210", "ap_ip": "", "app": "pdu",
                             "arch": "esp32", "uptime": 3}