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March 3, 2011
Product WRL-08687 |
about a year ago
Some users have posted messages indicating they’ve had trouble using the long-distance, Pro version XBee modules with XBee Explorer. Here are some tips that might help.
Before USB device enumeration takes place, only 100 mA is supplied to each device on the USB bus. During device enumeration, a device can request more than that (up to 500 mA). Not all USB ports and hubs can honor that request, especially if you’re using an external hub that is powered by a USB port on the PC. When in doubt, use a heavy duty hub that is powered from an AC adapter.
The USB “power descriptors” in the XBee Explorer’s FT232RL chip are configured to the factory default value of 90 mA. This works fine for the regular XBees, but not for the Pro versions, since they need more power when transmitting. To make the FT232RL request more than that from the USB hub or PC port, you can run the free FTDI ft_prog.exe utility to reconfigure the FT232RL power descriptors. This app note describes how to install and use ft_prog.exe -
The app note says you need to install their special D2XX drivers but on 64-bit Windows 7, I found that I didn’t have to do that. All I did was to launch ft_prog.exe, made it scan my USB ports to find the FTDI device, and changed the “Max Bus Power” value under USB Config Descriptors from 90 to 265 mA, since the Series 1 XBee Pro 802.14.5 module I’m using draws 250 mA when transmitting and the FT232RL itself draws another 15 mA. Some of the really long-distance, high-power XBee modules may require more than that.
After unplugging and replugging the XBee Explorer to confirm that it retained the new power setting, Windows displayed the usual “Installing device driver” pop-up message and said it
successfully installed a driver for the new device. This is to be expected because when the FT232RL’s descriptors change, Windows thinks it’s a new device.
Hope it helps,
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