This guide explains use of Texas Instruments WL1831 modules for WiFi and Bluetooth, instead of Wi2Wi's W2CBW0015 module. The aim of this guide is to highlight the key differences and make the transition between these modules as easy as possible.
The Overo AirSTORM-Y, FireSTORM-Y, and Iron STORM-Y modules differ from the corresponding Overo Air, Fire, and Iron STORM-P COMs only based on the module providing wireless connectivity. All Overo STORM-Y and Overo STORM-P COMs provide WiFi (802.11b/g/n), including access point mode, as well as Bluetooth (v3.0 or better) via a single antenna. The Overo STORM-Y COMs use the WL1831 module from the Texas Instruments WiLink 8 series, while the Overo STORM-P COMs use Wi2Wi's W2CBW0015 module containing a Marvell SD8787 chipset. While functionally speaking these Overo product-lines are very similar, some external electrical, and software changes that may be relevant to customers migrating from Overo STORM-P to Overo STORM-Y are summarized below:
- Wi2Wi W2CBW0015 module: https://pubs.gumstix.com/documents/Approvals/Wi2Wi/W2CBW0015/
- Texas Instruments WL1831 (WL18xx) module: http://processors.wiki.ti.com/index.php/WL18xxMOD_Certificates
- The footprint, dimension, and temperature specifications of the COM are unchanged
- Visually, the wireless module on the Overo STORM-Y series is enclosed in a metallic, silver-colored package; on the Overo STORM-P COMs, the module is in a black, plastic package
- The position of the antenna connector has moved by 1mm
- The Overo STORM-Y series COMs do not have a blue LED (D1) indicating WiFi activity
- No electrical changes are needed when interfacing with the COM
- The wireless module on the '-P' COMs interfaces both Wifi and Bluetooth functionality via an SDIO to the processor
- The wireless module on the '-Y' COMs uses SDIO for Wifi and a UART for Bluetooth
- Physical and electrical details are summarized in the Overo System Reference Manual at http://gumstix.org/images/overo_signals_latest.pdf.
- If you are using Yocto 1.7 (Dizzy) or Ubuntu images from Gumstix (https://www.gumstix.com/software/software-downloads/), no changes are required - the images support both series of COMs
- The u-boot Bootloader (i.e. the MLO and u-boot.img files) doesn't require any changes
- Support for the WiLink 8 chip is added on Gumstix's Linux 3.17 branch (https://github.com/gumstix/linux/tree/yocto-v3.17.y). This is the recommended baseline kernel for Overo STORM-Y COMs
- The Wilink8 module needs the CONFIG_BT_WILINK, and CONFIG_WL_TI options
- The Wi2Wi module needs the CONFIG_BT_MRVL_SDIO and CONFIG_MWIFIEX_SDIO options
- The Wilink8 module needs different firmware (see https://github.com/gumstix/meta-gumstix/commit/43f62462d709297a9ac3823b9fe2fe64d155bf10)
- In userspace, the Wilink8 Wifi interface appears as 'wlan0' where, by default, the Wi2Wi Wifi interface appears as 'mlan0'. Gumstix Yocto images present both interfaces as 'wlan0' working around this non-standard choice.
- As the Wilink8 bluetooth interface is available via the ttyO1 serial port, userspace must 'hciattach' to this port. Gumstix Yocto images do this automatically.