I got also an Error: WARNING: library ArduinoModbus claims to run on megaavr, samd, mbed_nano, mbed_portenta, mbed_opta architecture(s) and may be incompatible with your current board which runs on avr architecture(s).

WARNING: library ArduinoRS485 claims to run on samd, mbed_portenta, mbed_opta, mbed_nano, renesas_uno architecture(s) and may be incompatible with your current board which runs on avr architecture(s).

In file included from c:\Users\gv\Documents\Arduino\libraries\ModbusMaster\src/ModbusMaster.h:58,

from D:\AR4_teensy41_sketch_v5.1\AR4_teensy41_sketch_v5.1.ino:71:

c:\Users\gv\Documents\Arduino\libraries\ModbusMaster\src/util/crc16.h:71:17: warning: 'uint16_t crc16_update(uint16_t, uint8_t)' defined but not used [-Wunused-function]

71 | static uint16_t crc16_update(uint16_t crc, uint8_t a)

| ^~~~~~~~~~~~

c:\Users\gv\Documents\Arduino\libraries\ModbusMaster\src\ModbusMaster.cpp: In member function 'uint8_t ModbusMaster::requestFrom(uint16_t, uint16_t)':

c:\Users\gv\Documents\Arduino\libraries\ModbusMaster\src\ModbusMaster.cpp:94:27: warning: 'read' is used uninitialized [-Wuninitialized]

94 | _u8ResponseBufferLength = read;

| ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~

Opening Teensy Loader...

Memory Usage on Teensy 4.1:

FLASH: code:204064, data:18376, headers:8980 free for files:7895044

RAM1: variables:23200, code:201352, padding:28024 free for local variables:271712

RAM2: variables:12416 free for malloc/new:511872 Please help Guenter