With the emerging popularity of Internet of Things technologies and standards, many devices today are being connected to the internet or a cell phone via WIFI (802.11 b, g, etc.).
This project was to design an easy economical way to add WIFI capabilities to work with an existing product which used a simple micro-controller.
TechNich solutions design made use of a mini UART to WIFI converter board which turned out to be quite economical (less than $10 in small quantities). The UART to WIFI converter is a small certified module that installs on a circuit board. The circuit board was designed and laid out by the TechNich Solutions engineering group. Engineers had to design the PCB and trace layout for very specific requirements to maximize the efficiency of the on board WIFI antenna. In order to simplify FCC certification, a pre certified module was chosen so that FCC certification only consists of an unintentional radio certification. This significantly reduces the WIFI effort necessary.
Because WIFI communications require a TCP stack, the effort necessary to write the embedded software to implement a TCP stack can be reduced or eliminated by using a module that already incorporates a TCP stack. This enables the software engineer to focus on the application and not have to learn TCP communications in detail. After completing the embedded software development using the WIFI module, the final product had some excellent WIFI capabilities / features.
- WIFI Access Point (AP) mode. AP mode enables the board to work like a router. Any cell phone or PC would simply connect to the board wirelessly as it would any other router. This enables any PC, IPhone, or Android Phone to get data from the board on a real time basis.
- WIFI STA (stationary) mode. Stationary mode enables the board to connect wirelessly to any router. With STA mode, the board connects to the internet through a router with no smart phone or PC needed and thus has IoT capabilities. Since the product that this board was used in was also portable, TechNich Solutions engineers were able to program software to actually memorize routers and connect to a router the next time the device was in its vicinity.
- WPS mode – The board also provides WPS mode to enable fast easy entry of the routers SSID and password without a display. Just push a button on the router and supply power to the WIFI board and upon power-up, the SSID and password are entered. This enables STA mode to work effectively as a display is not required to configure the SSID and password necessary to connect
Real Time Clock
This board included a real time clock chip and battery backup. This enabled the host micro-controller to keep accurate track of time even when the power was off to the host micro-controller. Engineers interfaced to the clock using the I2C bus and with some special low current charging circuits, were able to charge a lithium battery enough to last for over 20 days when unplugged.
Switching Power Supply – Less Heat.
This board was powered by a 14 volt power supply. In order to keep down the power requirements of the board and reduce the heat generated by the board, a switching voltage regulator was incorporated into the design. By designing in some control circuitry in conjunction with the regulator, a low power mode was added which enabled the entire WIFI to be powered down and consume no power when not in use.
This board was designed to fit in a very small space so mounting of components became very critical. The board was about 25 mm by 40 mm.
When completed, this board supplied state of the art WIFI capabilities for a very reasonable price and a very small size. By making use of a pre certified module with a complete TCP stack, the effort to add WIFI can be reduced substantially
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