I'm working with MODBUS interface, based on a usb dongle which converts usb to RS485, then, in my board the rs485 half duplex is passed to max3362, as shown.
The data is passed to NXP K64 controller. My problem is that at the end of the modbus package the CPU is sending there's sometime an extra byte which causes the receiver to show an error. For example: This is the data the controller should be sending to the host: 0B 03 02 0F FF 65 F5. The bold 65 F5 is the crc.
Instead, sometime, it sends: 0B 03 02 0F FF 65 F5 C0
So, apparently, there an extra byte C0, which causes an error at the host side. I've tried with various USB dongles, at some, it seems ok, at some, it seems there's an error. I do not know what is the cause of the error, is it the board, FW, or dongle? Any ideas? I'm really stuck here.