<modbus.h> not found

[Manuel]

Hello, 

I tried doing:
cd ~ 

git clone git://github.com/stephane/libmodbus 

cd libmodbus 

./autogen.sh 

./configure --enable-static 

make 

sudo make install 

sudo cp ./src/.libs/libmodbus.a /usr/local/lib/

Now I have a libmodbus.a file in /usr/local/lib/.

Now I want to install mbrtu:


cd ~
git clone https://github.com/gitaeuber/mbrtu
cd mbrtu
make
sudo make install

But after make I get the error: 

In file included from mbrtu.c:22: mbrtu.h:25:12: fatal error: 

modbus.h: No such file or directory 25 | #include <modbus.h>

 compilation terminated. make: *** [Makefile:9: mbrtu] Error 1

I tried to add a modbus.conf to /usr/local/lib/ at /etc/ld.so.conf.d and reload it with 

sudo ldconfig

Sadly, my system still does not know about a libmodbus library.

Can someone help me? Debian linux