Drip v2

Drip irrigation controller

Table of contents

• Introduction
• Building instructions
• WiFi connectivity
  • UDP command messages
• Directory tree
• Hardware

Introduction

This drip irrigation controller was designed to control one relay for a water electrovalve and a second relay for ornament lights. Both relays may be configured for independent one-time-a-day activation to remain active during a configurable time. The frequency in terms of days between activations is also configurable. Any of the relays may be disabled which will stop their future scheduled activations.

A default configuration is applied at building time (edit files 'CMakeLists.txt', 'timers_default_data.cmake', and 'wlan_setup_data.cmake' to change it). The controller configuration (get and set) and manual activation may be done remotely through the wifi connection with simple UDP messages exchange.

This is the second controller I've built for my house plants. The first was written in Python in a rush before going out on a trip and worked perfectly. It had a dot matrix screen with a setup menu through microswitches; a real-time clock module, etc. But some years later it hangs a lot, outdoor installation always takes its toll.

So I've decided to implement a new version that loses the screen in favor of a WiFi connection for keep-alive signaling against a server, configuration and commands.

This repository includes all the code and scripts to built the program in a Raspberry Pi Pico (1) W board. The schematics for the external hardware is also included.

Luis Luque - 2025

Building instructions

REMEMBER: This code was made for and tested on a Pico W (first family of the Raspberry Pi Pico series). Use at your own risk in other platforms.

Clone repository from:

https://github.com/lluque42/drip_irrigation_controller.git

Two files are included to allow an easy customization:

• wlan_setup_data.cmake.template (rename to wlan_setup_data.cmake)
  • To enter the wifi SSID, password.
• timers_default_data.cmake
• To enter the time of the day, frequency and duration for the relays activation.

Create a build directory and enter to it:

drip_irrigation_controller $ mkdir build
drip_irrigation_controller $ cd build
drip_irrigation_controller/build $

Once inside, execute cmake against the parent directory (where the CMakeLists.txt is):

drip_irrigation_controller/build $ cmake ..
drip_irrigation_controller/build $

If no errors occurred, then a Makefile file should have been created in the build directory. Execute it to build the binaries.

drip_irrigation_controller/build $ make

If everything ok, a number of binary files should've been produced, among them a drip.elf or drip.uf2 ready to be loaded into the Pico W board.

For building the tests tool, see the Wifi connectivity section.

If some error occur check the pre-requisites:

• The PICO_SDK_VARIABLE environment variable should exist and point to the root of the pico-sdk directory.
• Is your board really a Pico W (first generation)?
• ? TODO

WiFi connectivity

The microcontroller can connect to a wireless network if the correct settings were edited in the wlan_setup_data.cmake file (a template for this file is provided, just write your settings and rename the file).

A static IPv4 address must be provided, as well as an UDP port (a high non-common one to avoid issues). This is necessary for the controller to act as a simple text UDP server. That is, it will open the UDP port listening for incoming messages. A set of message formats define commands and responses that may be sent to the controller and back.

The messages are plain-text ASCII, human readable, strings (without the NUL termination), that is, a string sent as the payload of the UDP datagram.

A simple, dirty client (and a server) written to debug this program is included as a git sub-module in:

drip_irrigation_controller/test/udp_tx_rx

Since it is a submodule it should be initialized from the drip_irrigation_controller root directory by doing:

drip_irrigation_controller $ git submodule update --init --recursive

After that, both the client and server can be build with:

drip_irrigation_controller/test/udp_tx_rx $ make

Which places the binaries in the bin folder.

To use the client to communicate over the wifi with the irrigation controller (assuming the default values in the wlan_setup_data.cmake.template) just do:

.../test/udp_tx_rx/bin $ ./udp_client 192.168.1.69 1234

This will receive input from the stdin for the user to send text to the controller.

The commands, their formats, and the expected replies are the following:

UDP command messages

Below are the recognized command messages and their replies. The client just need to write and read this as the payload of UDP messages to/from the controller that acts as a server on the IP address and UDP port set in the wlan_setup_data.cmake at build time.

• Set datetime: SET:DATETIME:YYYY:MM:DD:dotw:HH:mm:SS dotw: Day of the week 0-6. Sunday is 0.
• Set water timer parameters: SET:WATER:WTODHH:WTODmm:WTODSS:WEXD:DOW TOD: Time of day when activation should occur. EXD: Every X days, the X. Days between activations. DO: Duration of activation.
• Set lights timer parameters: SET:LIGHTS:LTODHH:LTODmm:LTODSS:LEXD:DOL TOD: Time of day when activation should occur. EXD: Every X days, the X. Days between activations. DO: Duration of activation.
• Get datetime: GET:DATETIME Response example: 2025:8:15:5:21:2:52 (see SET:DATETIME format).
• Get water relay current configuration: GET:WATER Response example: 21:0:0:1:120:2025:8:15:5:21:0:0 That is: Time of day: 21:0:0 Every X days: 1 Duration (sec): 120 Next activation scheduled: 2025:8:16:6:21:0:0 (see SET:DATETIME format).
• Get lights relay current configuration: GET:LIGHTS Response example: 21:0:0:1:10800:2025:8:15:5:21:0:0 See GET:WATER format.
• Manual on lights. MANUALON:LIGHTS
• Manual off lights. MANUALOFF:LIGHTS
• Manual on water. MANUALON:WATER
• Manual off water. MANUALOFF:WATER
• Timed on lights (Force turn on for the duration configured). TIMEDON:LIGHTS
• Timed on irigation (Force turn on for the duration configured). TIMEDON:WATER

For non get commands, expect a response of "done" if it was correctly processed or a custom human readable error message.

Directory tree

TODO

./  
├── .gitignore				(to prevent undesired files to be stagged)
├── Doxyfile				(doxygen config file for doc generation)  
├── Makefile				(use 'make help' for instructions)  
├── README.md				(brief documentation)  
├── doc/					(documentation extracted from comments in .h)  
│   ├── html/				(html documentation)  
│   │   ├── ...  
│   │   ├── index.html		(entry point for html documentation)  
│   │   ├── ...  
│   └── man/				(man pages documentation)  
│       └── man3/  
│           └── ...			(example of use: 'man -l ft_string.h.3')  
├── include/				(directory for public header files (.h))  
│   ├── ...  
│   └── ...  
├── src/					(dir for source code and private header files)  
│   ├── ...  
│   │   ├── ...  				
│   │   └── ...  
│   └── ...					(may be structured in several directories)  
│       ├── ...  
│       └── ...  
├── lib/					(external libraries)  

Hardware

TODO

Volts across led: 2,5 V With a 10K resistance and driven through the 2n3904 (100KOhm base to gpio)

With USB 5V directly fed, the relay coil consumes 70mA The pico restarts everytime te coil de-energizes, the diode requirement is real.

Had to replace the 100K base resistor with a 10K because with the realy coil current I guess the transistor couldn't remain polarized.