After spending some time investigating the MicroChip RN171 802.11 b/g Wireless LAN Module, I discovered that is is
not recommended for new designs.
MicroChip offers a new improved product (the
ATWINC1500) that, remarkably enough, is significantly cheaper than the RN171, and should perform better. One downside for our current design: the ATWINC1500 uses SPI to communicate with the host computer, instead of UART. The ATmega328P has SPI support, so we could adapt to the new product, but...
MicroChip is not the only game in town. STMicroelectronics offers a competing module (the
SPWF01) that seems to meet MicroChip's new product's spec, and supports UART and has its own built-in antenna, and some other cool features, like over-the-air updates. Prices seem to be in the under $20 range, some closer to $15.
I haven't decided on the best WLAN WiFi module yet; there is still some investigating to do. But one thing I'm becoming more convinced of is that a WiFi module and a portable smart device running an app, are a better option than building our own Control Head. A smartphone or tablet offers everything that our Control Head design has, only better integrated, more powerful, more portable, and for most folks much less expensive. The Control Head would cost close to $100 to build, and probably considerably more if fully loaded with GPS, digital compass, real-time clock, and a more powerful processor capable of handling all the data from those peripherals.
If you already own a smartphone or suitable tablet, then there would be no added cost for you: just download a free app. If you do not own a smart device, you can
purchase a used one, probably for less than the cost of building a less-capable Control Head... and no surface mount soldering! No cellular plan would be required either; WiFi and GPS will function on a smartphone without an active SIM card.
I will add a WiFi module option to the transmitter design. And I'm leaning toward mothballing the Control Head concept, and focusing instead on adding WiFi capability to the receiver, and a USB power port so that a smartphone can be charging while being used as part of the receiver. Work already done on the Control Head would remain available, should anyone want to use it, or a portion of its design.
This change in plans would alter the design of a 3D chassis for the receiver: instead of an LCD display and pushbuttons, we'll want perhaps a flat location to velcro a smartphone and have it protected from the elements, yet have its touchscreen accessible. Perhaps an Otterbox could be velcro'd in place?
As always, I welcome comments, concerns, or alternative ideas.