doc: more details in manual C code gen example

Author: franckgaga

Project.toml

@@ -1,6 +1,6 @@
 name = "ModelPredictiveControl"
 uuid = "61f9bdb8-6ae4-484a-811f-bbf86720c31c"
-version = "2.4.1"
+version = "2.4.2"
 authors = ["Francis Gagnon"]
 
 [deps]

docs/src/manual/linmpc.md

@@ -297,7 +297,8 @@ Note that measured disturbances are assumed constant in the future by default bu
 ## Generating C code
 
 The [`LinearMPC.jl`](@extref LinearMPC) package extension provides code generation
-capabilities to export the controller as optimized C code. First, install the package with:
+capabilities to export the controller as optimized and standalone C code. First, install the
+package with:
 
 ```test
 using Pkg; Pkg.add("LinearMPC")
@@ -308,6 +309,7 @@ The feedforward MPC controller can be converted to a [`LinearMPC.MPC`](@ref) obj
 ```@example 1
 import LinearMPC
 c_mpc_d = LinearMPC.MPC(mpc_d);
+nothing # hide
 ```
 
 We test the converted controller in closed-loop to verify that it behaves identically to the
@@ -350,11 +352,43 @@ can now generate the C code using:
 LinearMPC.codegen(c_mpc_d; dir="codegen", fname="mpc_funcs")
 ```
 
-The three C functions to call at each control periods are declared in the generated file
-`codegen/mpc_funcs.h`:
+The three C functions to call at each control period are declared in the generated
+`codegen/mpc_funcs.h` file, and they receive pointers of `c_float` arrays:
 
 ```C
-void mpc_correct_state(c_float* state, c_float* measurement, c_float* distrubance);  
+void mpc_correct_state(c_float* state, c_float* measurement, c_float* disturbance);  
 int mpc_compute_control(c_float* control, c_float* state, c_float* reference, c_float* disturbance);
 void mpc_predict_state(c_float* state, c_float* control, c_float* disturbance);
 ```
+
+For example, on Linux, you can add the following code in a new `main.c` file:
+
+```C
+#include "mpc_funcs.h" 
+#include <stdio.h>
+int main(){
+    // initialize arrays:
+    c_float u[2] = {20, 20};
+    c_float x[6] = {0, 0, 0, 0, 0, 0};
+    c_float r[2] = {50, 35};
+    c_float y[2] = {50, 30};
+    c_float d[1] = {20};
+    // execute one control period:
+    mpc_correct_state(x, y, d);
+    mpc_compute_control(u, x, r, d);
+    mpc_predict_state(x, u, d);
+    // print the computed control:
+    printf("The computed u value is: [%f, %f]\n", u[0], u[1]);
+    return 0;
+}
+```
+
+compile with using `gcc *.c -o main.bin` and run it with `./main.bin`. The printed `u` value
+should be identical to:
+
+```@example 1
+LinearMPC.set_state!(c_mpc_d, zeros(c_mpc_d.model.nx))
+x̂ = LinearMPC.correct_state!(c_mpc_d, [50, 30], [20])
+u = LinearMPC.compute_control(c_mpc_d, x̂; r=[50, 35], d=[20], uprev=[20, 20])
+println("The computed u value is: $(round.(u, digits=6))")
+```