Ok...I seems to got it working after configuring the GPIO pin for RTS. However, when I tried to communicate with modbus device, it gives me an "Checksum error in rtu mode". I am using minimal modbus library, and my code works fine when communicating between windows and my device.
I have tested my connection with the scope and it seems to get getting the correct output <https://lh3.googleusercontent.com/-F3TXY-EePnE/VZmQRb1SiZI/AAAAAAAAAFA/3WE1rRaXQis/s1600/tek00001.bmp> When testing it with the minimal modbus library, the slave ID, function code and payload data is correct. It just seems to have problem getting pass the error check. <https://lh3.googleusercontent.com/-e-xK1jzwGAM/VZmQk-l6ZrI/AAAAAAAAAFI/jGzceziRmiI/s1600/test3.py_write_reg255.bmp> I have configured my baud rate and parity check correctly, but I can't seems to figure out why it's giving me this checksum error. Anyone have any ideas where the problem is? On Saturday, July 4, 2015 at 6:29:11 PM UTC-4, A W wrote: > > Hello, > > I came across this tutorial on configuration for RS-485 serial > communication, but I am new to this and I need some clarifications on the > procedure. > > My beaglebone black is currently running on the latest Debian image > >> >> Linux beaglebone 3.8.13-bone70 #1 SMP Fri Jan 23 02:15:42 UTC 2015 armv7l >> GNU/Linux > > > > > On the website > http://inspire.logicsupply.com/2014/09/beaglebone-rs-485-communication.html > > Let's dive into the Kernel a bit to to see how RS-485 works in Linux; the >> standard steps to put a UART into RS-485 mode are: >> >> 1. Open the special tty file >> 2. Create a serial_rs485 struct and set the desired configuration >> values >> 3. Pass the configured struct to Kernel driver by using ioctl >> <http://man7.org/linux/man-pages/man2/ioctl.2.html> on the open >> serial port file descriptor >> >> I don't understand do these steps, where do I find the special tty file > and as well as creating the serial_rs485 struct. Can someone guide me > through this part? > > Thank you. > > > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
