Dear all,

I use a libmodbus rtu (libmodbus.org) in eclipse C++.

I correcly send a data by /dev/ttyS0 device, but my software stop running on library line code 

Are you aware of the fact that /dev/ttyS0 is the UART that is wired to the Arduino connectors? Moreover, its pins are multiplexed and need to be enabled first (see iot2000setup tool).

If you are on a 2040, you may want to look for ttyS2 (X30) or ttyS3 (X31).

PS: FD_SET is very unlikely to "stop" - it's a simple bitmask operation, nothing blocking on I/O. Maybe your debugger is providing misleading line numbers.

many thanks for your answer.

I know that /dev/ttyS0 is the same of UART(0) and it work very fine on my IOT2020. I have corerctly send a data in RS232 (TTL) mode and RS485 by a MAX485 chip on pin 0 & 1.

It work fine. If I send a data by a libmodbus I receive the data on the remote host by a 485<-->USB converter, but for the correctly working I have editing the modbus library ad I have disable the FD_SET(ctx->s, &rfds) line code.

I not understand why this line code not working on IOT2020.

Massimiliano

ok jan-k. Today I report the problem to libmodbus.org. Which modbus library is reccomended for IOT2000 use?

Massimiliano

New question published by eric00058 is split to a separate thread with the subject How to enable /dev/ttyS0 to be multiplexed, and where can find the iot2000setup tool?.

Best regards
Jen_Moderator