Legal Removal Request

Post: Hi, I'm having some troubles getting my Raspberry Pi 3+ to work with the IO Pi Plus. I'm testing this IO expander for the first time, but always get following error: "Failed to write to i2c device for write" Hardware: - Instead of using the OI Pi Plus header, I used a few jumper wires for now to connect 5V, GND, SDA and SCL from the Pi to the OI Pi Plus. - Also removed the solder jumper link already (I will use a seperate 5V power supply in the future). - No changes to addresses, so 0x20 for IC 1 (000) and 0x21 for IC 2 (001). [img]/docs/forumpost/fuzl8en.jpg[/img] Software: - Pre loaded NOOBS - Geany for C programming - Installed the ABElectronics libraries - ARM I2C enabled in raspi-config I'm using the demo-iopiread.c code (see also /ABElectronics_C_Libraries). When compiling, I first got 5 warnings "implicit declaration of function" (strerror, write, read, close and usleep), by adding #include <unistd.h> to ABE_IoPi.c, I removed 3 warnings (write, read, close). Don't know how to get the 2 other warnings go away, but not really my concern for now, I guess. When I run the demo code, one of the first things to execute is function [b]IOPi_init(0x20)[/b] [img]/docs/forumpost/o514if9.png[/img] Then function write_byte_data [img]/docs/forumpost/l06yzg4.png[/img] And then when the code fails [img]/docs/forumpost/gvfvbp2.png[/img] I'm searching for hours now and can't figure out why I can't write/communicate to the MCP23017 . I'm not even sure if this is an hardware or software problem. Can someone help me with this issue? Thank you in advance