CCS/AM3358: Profibus Master issue

Hello,

As Paula said above, I adapted TI's Profibus slave example to run on the BBB. I want to write a step-by-step guide for everyone to be able to do it, but I did not have the time yet.

Since you seem to know your way around TI-RTOS, the PDK and all I think I can try to quickly explain here and you can give it a go. It is actually quite easy.

First off, you need to introduce several modifications on the PDK (they are mostly pinmuxes and headers). I have attached below the files you need to change on a zip package with the same folder structure you have on your disk's PDK path.  If you want to know what these changes are about you can take a look at this application note which explains how to modify the console UART for the BBB. What you have to do for the Profibus examples is very similar, but it has to do with the PRUs, of course.

I cannot guarantee it, but I think you can safely overwrite the original files; nothing bad should happen. If you want to be sure, make a backup of the original files and/or folders (if something gets screwed, you can always reinstall the PDK, so the risk is quite low anyway).

Once you have the files in place you need to recompile the PDK with:

make all

If you've never done that before you'll have to set up the environment but that's quite straight forward (you can find excellent documentation on TI's wiki pages). Note that you need to recompile everything, including the bootloader. If you boot from an SD card you need to replace the existing MLO file with the new one that you just compiled and should be stored in the following folder:

pdk_am335x_1_0_15/packages/ti/starterware/binary/bootloader/bin/am335x-evm/gcc

You have to use the "_ti.bin" file, rename it to MLO and copy it to the SD card root folder. I prefer to send the APP file via UART (so I don't have to keep plugging and unplugging the SD card) so I use the image with the "uart" in its name as my MLO file (I boot from an SD card, but this way I only need to remove the card from the BBB once). If you prefer to boot the binary app from the SD card you'll have to use bootloader_boot_mmcsd_a8host_release.bin.

Now that you have your card ready to boot you need to compile the Profibus examples. I did not test the master (mainly because you need two BBBs, one to act as master and another one as slave or some other slave that I don't have at the moment) but I think it should work the same as the slave. After generating the project with the script provided and importing in CCS you have to change the project properties to the correct board (Beaglebone Black, and don't forget to change the platform to ti.platforms.beaglebone in the Products-->Platform menu), remove or rename the AM335x.lds file (this file contains the memory layout and it is generated if you build the example project using ti.platforms.evmAM3359 as the target platform, so it might not exist on your setup) and build the project. Then you can copy the app file to your SD card or upload the .bin (profibus_slave_AM335x_arm.bin for the slave) via UART.

As I said, I did not have the opportunity to test the Profibus Master yet but looking at the example I think the limitations referred to in the documentation (you cannot have more than three slaves on your bus and they all have to be the TI slave) are not hardcoded so you should be able to change the code to adapt it to your needs (depending on what your needs are that can take some time and effort).

Once you have the slave up and running and you can pair it with any PLC master using the GSD file included with the example. You can also use pyprofibus as a master, I've tested it and it works, but you have to use this branch, which is adapted for non-modular slaves (slaves with a single module. I'm not quite sure yet, but there seems to be a bug in pyprofibus that prevents it from running into data exchange if you define 8-byte-long blocks on your slave. That is, unfortunately, the default size of TI's example, so you might want to change that (you need to change it both on the GSD and on main.c, see section 4.4 here for details.

On the hardware front, you have to use the following wiring: output messages from the slave (and to be able to change inputs and send extended diagnostic frames) will be displayed on UART0, which is the one with male molex pins. This picture should help you set it up:

The Profibus link will be through UART1:

-UART1_TX is on P9 pin 24, to be connected to the RS485 transceiver Drive Input (DI)

-UART1_RX is on P9 pin 26, to be connected to the RS485 transceiver Read Output (RO)

-GPIO_1_25 on P9 pin 27, this pin will toggle the direction control line on the bus and it must be connected to the Drive Enable (DE) on the transceiver

-The Read Enable (~RE, inverted) must be connected to GND (on the BBB board or on the master's side, both must be connected together)

-For the power supply of the transceiver, you can use P9 pin 5

I know these instructions might not be good enough depending on your experience, just write back if you encounter any roadblocks.

Good luck.

EDIT:  As discussed in your other question, if you try to build the libraries using the files in the zip archive attached below you will get an undefined symbol error that you can fix copying the header with:

/opt/ti/pdk_am335x_1_0_15/packages# cp ./ti/board/src/icev2AM335x/include/board_internal.h ./ti/board/src/bbbAM335x/include/board_internal.h

pdk_am335x_1_0_15.zip