Schematic for LoRa soil monitor Reference Design: This is a LoRa...

LoRa Soil Monitor Design Overview

flux

0:27

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Project

Short answer: this design conditions a sensor signal with the MAX40005 and reads it on the MCU.

From the schematic:

Sensor input path:
- The soil probe connects at the IN net portal, then through R5 to the nano-power amplifier/comparator IC1 input (Net 22 → IC1:IN).
- The amplifier’s output (IC1:OUT) is on Net 17, which goes to the MCU’s PA8 pin on U2. C3 is tied to that path (to OUT and GND) to filter noise.
- C4 provides local rail decoupling for the analog stage.

What this implies functionally:

The soil probe changes its electrical characteristics with moisture (typically resistance or conductivity). That varying signal is presented through R5 into IC1.
IC1 conditions it and produces a clean logic/analog level the MCU can read on PA8. With suitable firmware, PA8 can:
- Use a digital threshold (treat IC1 as a comparator) for wet/dry or multi-level thresholding.
- Or sample as an analog input (if PA8 is configured as ADC on L0 variant) for quasi-analog moisture level, depending on MCU pin capabilities chosen in firmware.

Important caveats:

I do not see an explicit AC excitation or true resistive bridge that is common for corrosion-free soil sensing. As-is, this likely uses a simple DC-based measurement, which can work but may cause probe electrolysis over time.
There is no obvious sensor connector net labeled specifically for a two-electrode probe except the IN line plus GND. That suggests a single-ended measurement versus ground.

If you share how your probe is connected (two-wire resistive vs. capacitive pad), I can recommend:

For resistive probes: low-duty-cycle AC excitation via GPIO and measure with an RC/ADC method to reduce electrolysis, plus input protection.
For capacitive probes: drive an excitation signal and measure amplitude/phase or frequency using a timer/capture pin, or add a simple relaxation oscillator front end.

Would you like me to propose a concrete sensing front end and firmware readout approach for your specific probe type?

Ask about probe type

Request improved analog front end

Ask for AC excitation approach

Clarify MCU measurement method

Add connector and protection

71 days

Ready.

please explain what J1 does.

aneraovd

@copilot please explain what J1 does.

copilot

J1 is a connector, with the specific model being FTSH-105-01-L-DV-007-K, which is manufactured by Analog Devices. Connectors are hardware interfaces used for linking various electronic components together, providing the ability for electric current to flow between different regions of a circuit.

In the context of this project, J1 plays a vital role in enabling various functionalities. It has several pin connections, each with a specific role. Here are key pins and their functionalities:

Pins 1, 3, 5 are all tied to the main power rail 3V3, supplying the board and its components with the required power. Pin 1 is "VTref" (voltage reference), which indicates this pin might be used for setting a reference voltage for the system.
Pin 2 ("SWDIO/TMS") and Pin 4 ("SWDCLK/TCK") are connected to the SWDIO and SWCLK nets respectively. These are most likely used for Serial Wire Debug (SWD) interface which is used for debugging and programming the microcontroller (U2: STM32L031G6U6S).
Pin 10 ("~~RESET~~") is tied to the "RST" net, which typically would be used to reset the microcontroller or another digital system.
Pin 8 is named "NC/TDI", where NC usually denotes 'Not Connected', and TDI stands for "Test Data In" used in JTAG interface but since it's labeled as 'NC', it might not be used in this context.
Pin 6 ("SWO/TDO") could be used for Serial Wire Output or Test Data Output, both of which are used for debugging purposes.
Pin 9 ("GNDDetect") is likely tied to ground.

Please note that true functionality might depend on the overall system design and implementation.

Someone is typing...

please explain what U2 does.

cambrownobiwankenobi131140

@copilot please explain what U2 does.

Someone is typing...

LoRa_DIO0

Capacitance

1u F

SWCLK

LED_G

SPI1_MOSI

LoRa_RST

SPI1_CS

SWDIO

SPI1_CS

BOOT0

LED_R

LoRa_DIO0

USART2_RX

Capacitance

1u F

SPI1_SCK

SPI1_MISO

LED_B

USART2_RX

USART2_TX

Capacitance

10u F

LoRa_RST

SPI1_MOSI

ANT

RST

sensor

USART2_TX

Capacitance

1u F

SWDIO

RST

SPI1_SCK

SWCLK

BOOT0

SPI1_MISO

3V3

LED1

3V3

Resistance

220 Ω

Resistance

220 Ω

Resistance

10K Ω

Resistance

10k Ω

3V3

Resistance

220 Ω

3V3

BATT1

IC1

create a high level mermaid block diagram of sensor, LoRa\_DIO0, C4, 3V3, SWCLK,...

hinduraorohit1111

@copilot create a high level mermaid block diagram of sensor, LoRa_DIO0, C4, 3V3, SWCLK, LED1, LED_G, SPI1_MOSI, 3V3, 3V3, LoRa_RST, SPI1_CS, SWDIO, SPI1_CS, J1, BOOT0, LED_R, J2, LoRa_DIO0, USART2_RX, C3, SPI1_SCK, R4, SPI1_MISO, LED_B, R2, R3, USART2_RX, U2, R5, USART2_TX, C2, LoRa_RST, 3V3, SPI1_MOSI, IN, J4, LED_R, ANT, RST, sensor, USART2_TX, LED_G, LED_B, BATT1, 3V3, C1, R1, IC1, SWDIO, RST, 3V3, 3V3, SPI1_SCK, 3V3, U1, SWCLK, BOOT0, SPI1_MISO. Include key component's manufacturer part number in each block whenever possible.

copilot

Sure, here is the high-level block diagram using Mermaid syntax with the corrected math delimiters:

Image

Someone is typing...

Reviews

Electrical Rule Checks

Missing Footprints

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Overlapping Copper

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Invalid Layer

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Component Overrides • 8

	Designator	Ruleset
	＊｀REF｀＊	R2
	＊｀REF｀＊	C3
	＊｀REF｀＊	C3
	＊｀REF｀＊	R4
	＊｀REF｀＊	R1
	＊｀REF｀＊	R3
	＊｀REF｀＊	C2
	＊｀REF｀＊	C1

Airwires

Reports missing routed traces between pads in a net.

Deprecated Rules

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Layers with Multiple Fills

Reports layers that have multiple copper fills of different nets. Make sure the Connected Layers rule value of nets with fills is valid.

Floating Copper

Detect any via, trace or copper fill island that is not connected to any net.

Protected Intrusions

Reports intrusions from objects of other nets into polygons or fills that have the Protected layout rule applied.

Manufacturing

Manufacturer Part Number • 10

	Designator	MPN
	C1	None
	C2	None
	C3	None
	C4	None
	J2	None
	R1	None
	R2	None
	R3	None
	R4	None
	R5	None

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Passive Components

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Capacitor Voltage Rating

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Checks that capacitors have appropriate voltage ratings to prevent overheating and ensure reliable circuit operation.

Ground
A common return path for electric current. Commonly known as ground.
jharwinbarrozo
20.5M
Net Portal
Wirelessly connects nets on schematic. Used to organize schematics and separate functional blocks. To wirelessly connect net portals, give them same designator. #portal
jharwinbarrozo
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Power Net Portal
Wirelessly connects power nets on schematic. Identical to the net portal, but with a power symbol. Used to organize schematics and separate functional blocks. To wirelessly connect power net portals, give them the same designator. #portal #power
jharwinbarrozo
11.4M
Generic Resistor
A generic fixed resistor for rapid developing circuit topology. Save precious design time by seamlessly add more information to this part (value, footprint, etc.) as it becomes available. Standard resistor values: 1.0Ω 10Ω 100Ω 1.0kΩ 10kΩ 100kΩ 1.0MΩ 1.1Ω 11Ω 110Ω 1.1kΩ 11kΩ 110kΩ 1.1MΩ 1.2Ω 12Ω 120Ω 1.2kΩ 12kΩ 120kΩ 1.2MΩ 1.3Ω 13Ω 130Ω 1.3kΩ 13kΩ 130kΩ 1.3MΩ 1.5Ω 15Ω 150Ω 1.5kΩ 15kΩ 150kΩ 1.5MΩ 1.6Ω 16Ω 160Ω 1.6kΩ 16kΩ 160kΩ 1.6MΩ 1.8Ω 18Ω 180Ω 1.8KΩ 18kΩ 180kΩ 1.8MΩ 2.0Ω 20Ω 200Ω 2.0kΩ 20kΩ 200kΩ 2.0MΩ 2.2Ω 22Ω 220Ω 2.2kΩ 22kΩ 220kΩ 2.2MΩ 2.4Ω 24Ω 240Ω 2.4kΩ 24kΩ 240kΩ 2.4MΩ 2.7Ω 27Ω 270Ω 2.7kΩ 27kΩ 270kΩ 2.7MΩ 3.0Ω 30Ω 300Ω 3.0KΩ 30KΩ 300KΩ 3.0MΩ 3.3Ω 33Ω 330Ω 3.3kΩ 33kΩ 330kΩ 3.3MΩ 3.6Ω 36Ω 360Ω 3.6kΩ 36kΩ 360kΩ 3.6MΩ 3.9Ω 39Ω 390Ω 3.9kΩ 39kΩ 390kΩ 3.9MΩ 4.3Ω 43Ω 430Ω 4.3kΩ 43KΩ 430KΩ 4.3MΩ 4.7Ω 47Ω 470Ω 4.7kΩ 47kΩ 470kΩ 4.7MΩ 5.1Ω 51Ω 510Ω 5.1kΩ 51kΩ 510kΩ 5.1MΩ 5.6Ω 56Ω 560Ω 5.6kΩ 56kΩ 560kΩ 5.6MΩ 6.2Ω 62Ω 620Ω 6.2kΩ 62KΩ 620KΩ 6.2MΩ 6.8Ω 68Ω 680Ω 6.8kΩ 68kΩ 680kΩ 6.8MΩ 7.5Ω 75Ω 750Ω 7.5kΩ 75kΩ 750kΩ 7.5MΩ 8.2Ω 82Ω 820Ω 8.2kΩ 82kΩ 820kΩ 8.2MΩ 9.1Ω 91Ω 910Ω 9.1kΩ 91kΩ 910kΩ 9.1MΩ #generics #CommonPartsLibrary
jharwinbarrozo
1.5M
Generic Capacitor
A generic fixed capacitor ideal for rapid circuit topology development. You can choose between polarized and non-polarized types, its symbol and the footprint will automatically adapt based on your selection. Supported options include standard SMD sizes for ceramic capacitors (e.g., 0402, 0603, 0805), SMD sizes for aluminum electrolytic capacitors, and through-hole footprints for polarized capacitors. Save precious design time by seamlessly add more information to this part (value, footprint, etc.) as it becomes available. Standard capacitor values: 1.0pF 10pF 100pF 1000pF 0.01uF 0.1uF 1.0uF 10uF 100uF 1000uF 10,000uF 1.1pF 11pF 110pF 1100pF 1.2pF 12pF 120pF 1200pF 1.3pF 13pF 130pF 1300pF 1.5pF 15pF 150pF 1500pF 0.015uF 0.15uF 1.5uF 15uF 150uF 1500uF 1.6pF 16pF 160pF 1600pF 1.8pF 18pF 180pF 1800pF 2.0pF 20pF 200pF 2000pF 2.2pF 22pF 20pF 2200pF 0.022uF 0.22uF 2.2uF 22uF 220uF 2200uF 2.4pF 24pF 240pF 2400pF 2.7pF 27pF 270pF 2700pF 3.0pF 30pF 300pF 3000pF 3.3pF 33pF 330pF 3300pF 0.033uF 0.33uF 3.3uF 33uF 330uF 3300uF 3.6pF 36pF 360pF 3600pF 3.9pF 39pF 390pF 3900pF 4.3pF 43pF 430pF 4300pF 4.7pF 47pF 470pF 4700pF 0.047uF 0.47uF 4.7uF 47uF 470uF 4700uF 5.1pF 51pF 510pF 5100pF 5.6pF 56pF 560pF 5600pF 6.2pF 62pF 620pF 6200pF 6.8pF 68pF 680pF 6800pF 0.068uF 0.68uF 6.8uF 68uF 680uF 6800uF 7.5pF 75pF 750pF 7500pF 8.2pF 82pF 820pF 8200pF 9.1pF 91pF 910pF 9100pF #generics #CommonPartsLibrary
jharwinbarrozo
1.5M
Generic Inductor
A generic fixed inductor for rapid developing circuit topology. *You can now change the footprint and 3D model at the top level anytime you want. This is the power of #generics
jharwinbarrozo
15.1k
Terminal
An electrical connector acting as reusable interface to a conductor and creating a point where external circuits can be connected.
natarius
RMCF0805JT47K0
47 kOhms ±5% 0.125W, 1/8W Chip Resistor 0805 (2012 Metric) Automotive AEC-Q200 Thick Film #forLedBlink
jharwinbarrozo
1.2M
875105359001
10uF Capacitor Aluminum Polymer 20% 16V SMD 5x5.3mm #forLedBlink #commonpartslibrary #capacitor #aluminumpolymer #radialcan
jharwinbarrozo
1.2M
CTL1206FYW1T
Yellow 595nm LED Indication - Discrete 1.7V 1206 (3216 Metric) #forLedBlink
jharwinbarrozo
1.1M

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LoRa soil monitor Reference Design

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Properties

License

https://creativecommons.org/licenses/by/4.0/

Availability & Pricing

Distributor		Qty 1
	Digi-Key	$8.35–$8.72
	LCSC	$5.11
	Mouser	$29.60

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LoRa soil monitor Reference Design.png

id=LoRa soil monitor Reference Design

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