FPGA Irrigation Simulator

irrigation_system.vVerilog HDL

// PROJECT  : Automatic Irrigation System
// SENSOR   : JXCT Soil 7-in-1 Modbus RS485 (5V)
// DEVICE   : Xilinx FPGA XC7A35T Artix-7

module irrigation_system (
    input  wire        clk,          // FPGA system clock
    input  wire        rst,          // Active-high reset
    input  wire        rx,           // RS485 UART receive line (Modbus)

// 7 Sensor Parameters (decoded from Modbus RS485 frame)
    input  wire [11:0] moisture,     // Soil moisture    (0–1000, unit: 0.1%)
    input  wire [11:0] temperature,  // Soil temperature (0–800,  unit: 0.1°C)
    input  wire [11:0] ec,           // Electrical cond. (0–9999, µS/cm)
    input  wire [11:0] ph,           // Soil pH value    (0–140,  unit: 0.1)
    input  wire [11:0] nitrogen,     // Nitrogen (N)     (0–1999, mg/kg)
    input  wire [11:0] phosphorus,   // Phosphorus (P)   (0–1999, mg/kg)
    input  wire [11:0] potassium,    // Potassium (K)    (0–1999, mg/kg)

// Outputs
    output reg         pump,         // Water pump relay control
    output reg         led_green,    // Green LED: Pump ON
    output reg         led_red,      // Red LED:   Pump OFF / Alert
    output reg         alert,        // Alert: unsafe soil condition

// RS485 Modbus TX (for requesting next sensor read)
    output reg         tx,
    output reg [7:0]   modbus_cmd    // Modbus RTU command byte
);

// ─── THRESHOLD CONSTANTS (Pre-set in FPGA logic fabric) ──────────────────
// These are hardware constants — not variables.
// Simple sensor CANNOT provide all these parameters.
localparam MOIST_LOW    = 12'd300;   // Below 30.0% → DRY → Pump ON
localparam MOIST_HIGH   = 12'd700;   // Above 70.0% → WET → Pump OFF
localparam TEMP_MAX     = 12'd450;   // Above 45.0°C → Unsafe for irrigation
localparam EC_MAX       = 12'd2000;  // Above 2000 µS/cm → Soil salinity too high
localparam PH_LOW       = 12'd50;    // Below pH 5.0 → Acidic → Alert
localparam PH_HIGH      = 12'd85;    // Above pH 8.5 → Alkaline → Alert
localparam N_LOW        = 12'd50;    // Below 50 mg/kg → Nitrogen deficiency
localparam P_LOW        = 12'd30;    // Below 30 mg/kg → Phosphorus deficiency
localparam K_LOW        = 12'd100;   // Below 100 mg/kg → Potassium deficiency

// ─── STATE MACHINE STATES ────────────────────────────────────────────────
localparam IDLE         = 2'b00;
localparam READ_SENSOR  = 2'b01;
localparam PROCESS      = 2'b10;
localparam OUTPUT       = 2'b11;

reg [1:0] state;
reg [1:0] next_state;

// ─── INTERNAL CONDITION FLAGS ────────────────────────────────────────────
wire soil_dry;
wire soil_wet;
wire temp_safe;
wire ec_safe;
wire ph_safe;
wire nutrients_ok;
wire safe_to_irrigate;

// Condition logic (combinational)
assign soil_dry       = (moisture    <  MOIST_LOW);
assign soil_wet       = (moisture    >= MOIST_HIGH);
assign temp_safe      = (temperature <  TEMP_MAX);
assign ec_safe        = (ec          <  EC_MAX);
assign ph_safe        = (ph          >= PH_LOW)  && (ph <= PH_HIGH);
assign nutrients_ok   = (nitrogen    >= N_LOW)   &&
                        (phosphorus  >= P_LOW)   &&
                        (potassium   >= K_LOW);

// All environmental conditions must be SAFE before pump activates
assign safe_to_irrigate = temp_safe && ec_safe && ph_safe;

// ─── STATE REGISTER (Sequential) ────────────────────────────────────────
always @(posedge clk or posedge rst) begin
    if (rst)
        state <= IDLE;
    else
        state <= next_state;
end

// ─── NEXT STATE LOGIC (Combinational) ────────────────────────────────────
always @(*) begin
    case (state)
        IDLE:        next_state = READ_SENSOR;
        READ_SENSOR: next_state = PROCESS;
        PROCESS:     next_state = OUTPUT;
        OUTPUT:      next_state = IDLE;
        default:     next_state = IDLE;
    endcase
end

// ─── OUTPUT LOGIC (Multi-parameter decision) ─────────────────────────────
always @(posedge clk or posedge rst) begin
    if (rst) begin
        pump       <= 1'b0;
        led_green  <= 1'b0;
        led_red    <= 1'b1;
        alert      <= 1'b0;
        tx         <= 1'b1;
        modbus_cmd <= 8'h00;
    end
    else if (state == OUTPUT) begin

// UNSAFE CONDITION: Do NOT irrigate regardless of moisture
        if (!safe_to_irrigate) begin
            pump      <= 1'b0;
            led_green <= 1'b0;
            led_red   <= 1'b1;
            alert     <= 1'b1;   // ← Simple sensor CANNOT trigger this
        end

// SAFE + DRY: Activate pump
        else if (soil_dry && safe_to_irrigate) begin
            pump      <= 1'b1;
            led_green <= 1'b1;
            led_red   <= 1'b0;
            alert     <= 1'b0;
        end

// SAFE + WET: Pump OFF
        else if (soil_wet) begin
            pump      <= 1'b0;
            led_green <= 1'b0;
            led_red   <= 1'b1;
            alert     <= 1'b0;
        end

// Nutrient deficiency alert (no pump change, only flag)
        if (!nutrients_ok) begin
            alert     <= 1'b1;   // ← N/P/K — simple sensor has NO concept of this
        end

// Modbus command: request next sensor frame (RS485)
        modbus_cmd <= 8'h03;     // Modbus RTU function code: Read Holding Registers
        tx         <= 1'b0;      // Initiate next read cycle
    end
end

endmodule

constraints.ucfUCF Pin Map

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🔲 FPGA Device

FamilySpartan-6

DeviceXC6SLX9

PackageTQG144

Speed Grade-3

Logic Cells9,152

Flip-Flops11,440

I/O Pins102 (user)

Clock100 MHz

ToolXilinx ISE 14.7

BitstreamNot generated

📌 Pin Assignments

clk

LOC: V10

100 MHz Osc

rst

LOC: C9

Push Button

soil

LOC: T10

Sensor AO

pump

LOC: U16

Relay Drive

led_green

LOC: U18

LD0 Pump ON

led_red

LOC: M14

LD1 Pump OFF

📊 Resource Utilization

Slice LUTs12 / 5765 (0%)

Flip-Flops28 / 11440 (0%)

IOBs6 / 102 (6%)

TimingMET — 98.4 MHz

StatusNot programmed

Soil Moisture Sensor

Moisture Level50%

0 — Dry100 — Wet

Auto-cycle test

FPGA Threshold

Dry/Wet boundary50

soil_s: 1'b0 (DRY)

Component Map

Q1 NPN BC547 Transistor
R1,R2,R3 220Ω Resistors
M1 DC Motor (Water Pump)
D1 Green LED — Pump ON
D2 Red LED — Pump OFF

⚡ Xilinx ISE 14.7 — Program FPGA Device