Valvenode

ValveNode

ValveNode is a wired field-bus irrigation valve-control system for my Raspberry Pi farm automation stack.

This project is a continuation of the work described in Off-Grid Farm Automation with Raspberry Pi.

The irrigation side started with a Raspberry Pi, relay outputs, and conventional sprinkler valve wiring, described in Raspberry Pi Internet of Things - part 2: Controlling the Irrigation valves. That proved the basic idea: local software can control real irrigation hardware without a cloud service or proprietary controller. It also exposed the usual field problems: long wire runs, voltage drop, power loss, serviceability, and too many individual valve wires returning to one box.

I later experimented with more efficient solenoid drive hardware using a DRV103 in Not Another Sprinkler Valve Article. That design gives a conventional valve a strong opening pulse and then reduces average power with PWM, which matters for long wire runs and battery-backed operation.

As the farm kept expanding, the wiring problem started to matter more than the valve-control problem. Every new irrigation zone meant another long wire run back to the controller, more trenching, more splices, more voltage drop, and more things to troubleshoot later. At that point, spending a few extra dollars per valve for latching solenoids was worth it if it let the field wiring become a simple 4-wire RS-485 network.

ValveNode takes the next step: instead of pulling every valve wire back to the controller, it moves small controller cards out into the field.

A Raspberry Pi talks to a Valve Master over I2C. The Valve Master starts a 4-wire RS-485 field cable carrying power and data. Valve Node cards sit along that cable, and each card drives a local latching irrigation solenoid with a short polarity-controlled pulse.

The goal is simple: irrigation control that is local, wired, understandable, repairable, and expandable.

Overview

The project has two primary components:

• valvenode-master
  ATmega88PB-based I2C-to-RS-485 master controller.

  

• valvenode-slave
  ATtiny4313-based RS-485 valve node for controlling latching irrigation valves.

The upstream controller talks to the Valve Master over I2C. The Valve Master controls field power and communicates with downstream Valve Nodes over RS-485.

Latching Solenoids

ValveNode is designed around low-voltage DC latching irrigation solenoids. The initial supported solenoids are:

A latching solenoid is not powered continuously. The Valve Node drives it with a short polarity-controlled pulse through the H-bridge: one polarity opens the valve, the opposite polarity closes it, and then the output is turned off.

Project Goals

• Wired field-bus control for irrigation valves
• No cloud dependency
• No wireless dependency
• Local 12 V field-power switching
• Half-duplex RS-485 node communication
• AVR-based firmware that can be understood, built, and serviced
• KiCad hardware source included
• Separate master firmware, simulator, Linux test tool, and node firmware

Repository Layout

valvenode/
├── valvenode-master/
│   ├── docs/
│   ├── firmware/
│   ├── hw/
│   │   └── 1.0/
│   ├── sim/
│   └── test/
└── valvenode-slave/
    ├── docs/
    ├── firmware/
    ├── hw/
    │   ├── 1.0/
    │   └── 1.1/
    └── test/

Valve Master

Path:

valvenode-master/

The Valve Master is the central controller for the valve-node network.

It performs these jobs:

• Accepts host commands over I2C
• Controls switched 12 V field-bus power
• Sends RS-485 commands to downstream valve nodes
• Receives valve-node replies
• Maintains node discovery state
• Reports status and command results to the host
• Provides local visual status indication
• Exposes AVR ISP programming access

Default I2C address:

0x09

Address 0x08 is reserved for a separate power-control board, so 0x09 is used as the default Valve Master address.

Valve Master Hardware

Path:

valvenode-master/hw/1.0/

Important KiCad source files:

valvenode-master.kicad_pro
valvenode-master.kicad_sch
valvenode-master.kicad_pcb

The master board uses:

• ATmega88PB-AU
• MAX485-style RS-485 transceiver
• Relay-switched 12 V field-bus output
• FAULT input
• COMM and FAULT indicators
• AVR ISP header
• I2C host-side interface

Valve Master Firmware

Path:

valvenode-master/firmware/

Files:

makefile
valvenode_master.c

The firmware implements the production Valve Master behavior:

• I2C slave interface
• Register map
• Deferred command handling
• RS-485 transmit/receive control
• Field-bus power control
• Node discovery
• Valve-node command dispatch
• Result and reply registers
• Fault/status reporting

Directed RS-485 commands include timeout handling and retry behavior. A single missed node reply should not turn into an immediate hard failure on a slow irrigation field bus.

Build:

cd valvenode-master/firmware
make

Valve Master Simulator

Path:

valvenode-master/sim/

Files:

makefile
valvenode_master_sim.c

The simulator models the master command/register behavior for bench testing without hardware.

Build:

cd valvenode-master/sim
make

Valve Master Linux Test Tool

Path:

valvenode-master/test/

Files:

makefile
Doxyfile
src/

Source files:

I2C.cpp
I2C.hpp
LogMgr.cpp
LogMgr.hpp
TimeStamp.cpp
TimeStamp.hpp
Valve_master.cpp
Valve_master.hpp
main.cpp

The test tool is a Linux-side C++ program used to talk to the Valve Master over /dev/i2c-*.

The main C++ class is:

Valve_master

It wraps the Valve Master I2C register map and command model.

Typical responsibilities:

• Open the Linux I2C device
• Select the Valve Master I2C address
• Read and write registers
• Submit commands
• Wait for command completion
• Read command results
• Read reply registers
• Read discovered node map
• Query firmware versions
• Control field power
• Ping nodes
• Set valve/channel state

Build:

cd valvenode-master/test
make

Common valve commands:

./valve status
./valve power on
./valve power off
./valve who
./valve map
./valve ping 1
./valve set 1 1 on
./valve set 1 1 off
./valve channel 1 1 status
./valve version master
./valve version 1
./valve identify 1
./valve cancel

Provisioning commands:

./valve config
./valve assign 7
./valve move 7 8

Hammer Test

Path:

valvenode-master/test/hammer.sh

hammer.sh repeatedly exercises the full Valve Master path.

Test pattern:

power on
ping nodes
initial status nodes
loop:
  set ON nodes
  status nodes
  set OFF nodes
  status nodes
final status nodes
power off

Example:

cd valvenode-master/test
./hammer.sh 25
NODES="1 3 4 5 6" CHANNEL=1 ./hammer.sh 500

Optional settings:

CHANNEL=2 ./hammer.sh 25
VERBOSE=1 ./hammer.sh 25
VALVE_BIN=./valve ./hammer.sh 25
NODES="1 3 4 5 6" ./hammer.sh 25
RETRY_ON_FAIL=1 ./hammer.sh 25

Recent bench result:

500 loops
5 nodes tested: 1 3 4 5 6
channel 1
10,016 commands
0 failures
100% first-try pass rate

Generate local Doxygen docs:

cd valvenode-master/test
doxygen Doxyfile
open docs/html/index.html

Valve Master I2C Register Model

The host talks to the master through a small register map.

Important registers include:

REG_COMMAND
REG_STATUS
REG_ARG0
REG_ARG1
REG_ARG2
REG_RESULT
REG_POWER_STATE
REG_NODE_COUNT
REG_REPLY_NODE
REG_REPLY_CMD
REG_REPLY_ARG0
REG_REPLY_ARG1
REG_VERSION_HI
REG_VERSION_LO
REG_NODE_MAP

Important command values include:

CMD_POWER_ON
CMD_POWER_OFF
CMD_WHO
CMD_PING
CMD_SET_CHANNEL
CMD_GET_CHANNEL_STATUS
CMD_GET_NODE_VERSION
CMD_IDENTIFY
CMD_CANCEL
CMD_CONFIG
CMD_ASSIGN
CMD_CLEAR_ERROR
CMD_SET_ERROR
CMD_CLOSE_ALL

Important status bits include:

STATUS_BUSY
STATUS_ERROR
STATUS_POWER_ON

Important result values include:

RESULT_OK
RESULT_BAD_COMMAND
RESULT_BAD_NODE
RESULT_BAD_CHANNEL
RESULT_NODE_NOT_FOUND
RESULT_UNSUPPORTED_CHANNEL
RESULT_CONFIG_REQUIRED
RESULT_ADDRESS_IN_USE
RESULT_BUSY
RESULT_RS485_TIMEOUT
RESULT_RS485_BAD_CHECKSUM
RESULT_RS485_BAD_REPLY
RESULT_POWER_OFF

Valve Node

Path:

valvenode-slave/

The Valve Node is the remote field device. It receives RS-485 commands and drives a 12 V latching irrigation valve.

Core functions:

• Receive framed RS-485 commands
• Check destination address
• Respond to discovery and status commands
• Drive a latching valve using a polarity-controlled pulse
• Turn the H-bridge fully off after each pulse
• Report current logical valve state

Valve Node Hardware

Paths:

valvenode-slave/hw/1.0/
valvenode-slave/hw/1.1/

Important KiCad source files:

valvenode.kicad_pro
valvenode.kicad_sch
valvenode.kicad_pcb

The 1.1 hardware directory is the newer active revision.

The node hardware uses:

• ATtiny4313
• 5 V RS-485 transceiver
• VNH7100BAS / VNH7100BASTR H-bridge
• 12 V latching irrigation valve output
• 12 V field-bus input
• Local 5 V regulator
• Optional status LED

Basic field connection:

+12 V
GND
RS-485 A
RS-485 B

The design is intended for direct-burial irrigation cable.

Recommended cable:

• 18/4 acceptable for shorter runs
• 16/4 preferred for longer runs or higher node counts

Valve Node Power Architecture

The node receives 12 V from the field cable.

Power paths:

• 12 V directly feeds the valve driver supply
• 12 V feeds a local 5 V regulator
• 5 V powers the ATtiny4313 and RS-485 transceiver

Recommended protection and stability parts include:

• Bidirectional TVS across the 12 V input
• Bulk capacitance near the H-bridge supply
• 0.1 uF local decoupling at MCU and transceiver
• Additional 5 V bulk capacitance near the MCU
• Reverse-polarity protection where practical

For master-side field power switching, allow roughly 250 to 300 ms after switching on the 12 V field bus before sending node commands.

Valve Node Firmware

Path:

valvenode-slave/firmware/

Files:

makefile
valvenode.c
valvenode_example_commands.txt

The firmware target is the ATtiny4313.

Firmware responsibilities:

• UART receive
• RS-485 command parsing
• Address matching
• Optional checksum checking
• Valve open pulse
• Valve close pulse
• Status reporting
• Ping reply
• WHO discovery reply
• Safe H-bridge shutdown after each pulse

Build:

cd valvenode-slave/firmware
make

Valve Node Test Tool

Path:

valvenode-slave/test/

Files:

makefile
src/main.cpp

The vnode utility is used for direct bench testing of valve nodes over a serial port. It assumes the computer is connected to the RS-485 bus through a USB-to-RS-485 adapter.

This bypasses the Valve Master and talks directly to the nodes.

Build:

cd valvenode-slave/test
make

Example:

./vnode -d /dev/ttyUSB0 who
./vnode -d /dev/ttyUSB0 ping 1
./vnode -d /dev/ttyUSB0 open 1 1
./vnode -d /dev/ttyUSB0 close 1 1

Typical output:

$ ./vnode -d /dev/ttyUSB0 who
device: /dev/ttyUSB0
baud:   9600
tx: :FFW\r
rx: :01WB8  [checksum ok] node=1 WHO
rx: :02WB9  [checksum ok] node=2 WHO

vnode can also be used to configure a fresh node, assign its address, and verify that it answers before it goes into the field.

RS-485 Valve Node Protocol

The Valve Master and Valve Nodes communicate over a half-duplex RS-485 bus.

The node protocol is command/response. The master sends a framed command. A node replies only when addressed or when participating in a controlled discovery response.

Typical commands:

PING
STATUS
OPEN
CLOSE
WHO
IDENTIFY
CONFIG
ASSIGN
VERSION

Typical behavior:

• PING confirms node presence
• STATUS reports logical valve/channel state
• OPEN sends the open-polarity valve pulse
• CLOSE sends the close-polarity valve pulse
• WHO is used for node discovery
• IDENTIFY asks a node to identify itself
• CONFIG enters configuration behavior
• ASSIGN sets or changes a node address
• VERSION reports firmware version

Broadcast state-changing commands should be avoided unless explicitly implemented and safe.

Useful Linux I2C Commands

List I2C buses:

i2cdetect -l
ls -l /dev/i2c-*

Scan I2C bus 1:

i2cdetect -y 1

Look for the Valve Master at address 0x09.

Check user permissions for I2C:

groups
ls -l /dev/i2c-*

If needed, add the user to the i2c group on Linux:

sudo usermod -aG i2c $USER

Then log out and back in.

Development Notes

• The Valve Master default I2C address is 0x09.
• The Valve Master controls field-bus 12 V power.
• The Valve Nodes are not autonomous irrigation controllers.
• Valve Nodes execute direct command/response behavior.
• Latching valves must be driven with short pulses, not continuous power.
• H-bridge outputs must be turned off after each pulse.
• RS-485 bus direction control must be handled carefully to avoid bus contention.
• Field wiring should assume noise, voltage drop, wet boxes, lightning exposure, and field-service abuse.

Current Project Status

The repository currently contains:

• Valve Master hardware design
• Valve Master firmware
• Valve Master simulator
• Valve Master Linux I2C test tool: valve
• Valve Master hammer test: hammer.sh
• Valve Node hardware revisions
• Valve Node firmware
• Valve Node direct RS-485 test tool: vnode
• Protocol and design documentation

Current bench status:

• Valve Master can switch field power
• Valve Master can communicate with multiple valve nodes over RS-485
• Valve nodes respond to discovery, ping, set, and status commands
• hammer.sh has completed a 500-loop, 10,016-command bench test across five nodes with zero failures

Remaining validation:

• Confirm final latching-solenoid open/close polarity with real valve bodies
• Test final assembled boards in outdoor enclosures
• Validate longer real field-cable runs
• Continue field reliability testing before treating the system as deployed infrastructure