I’m proceeding to implement the following communication network but I would appreciate input on any issues I might expect.
Communications Network Description:
Briefly: a uC serial port connects wirelessly to a PC for continuous data exchange
In more Detail:
ATmel AVR AT32UC3 uC’s USB port connected to an FTDI VDIP1 (USB Host Controller).
VDIP1’s UART connected to 802.15.4 XBee’s UART (a.k.a Remote endpoint) that in turn communicates to another 802.15.4 XBee, which is connected to a PC via USB (XBee explorer board, a.k.a. Local XBee).
The AVR generates data that must be read continuously by software running on PC (lets call it the Filter SW, or just filter).
o AVR software has already been designed to use build-in USB port and I don’t want to change it. AVR’s port baud rate is 115200. AVR sw must be commanded to begin transmitting data. AVR software was designed without any knowledge of VDIP use, i.e. it normally connects directly to a PC.
o VDIP1’s baud rate is 9600 on power-up (can’t change this behavior), which is not compatible with AVR rate so a special “command mode” via its UART must be entered and used to change its baud to 115200.
To summarize: AVR is connected via USB to the USB to UART adapter (VDIP1). VDIP1’s UART connect to XBee’s UART. XBee’s exchange bytes wirelessly. Local XBee connect to Filter via USB. Baud rate from PC down to AVR must be made the same–115200 to communicate.
Assuming XBee modules are setup to start at 9600 baud, here is what I plan to do:
Upon Filter startup on PC, I will use Local and Remote XBee’s AT transparent mode to send commands to VDIP UART port to enter command mode and set it’s baud rate to 115200. The VDIP1 can now comm with AVR. Next, I will change Local XBee to API command mode and issue remote commands to Remote Endpoint to change it’s baud rate to 115200. Next, I will change Local XBee’s baud rate to 115200. Finally, I will issue commands that will, in turn, verify that I can communicate with Local XBee, Remote XBee, VDIP1 command mode, and then with the AVR. Prior to shutting down the wireless link I will propagate a baud rate reduction back to 9600, etc.
What really stinks is that the VDIP1 reverts back to 9600 baud when power cycled and I don’t want to establishing another uC between the Remote XBee module and the VDIP1 module.