# Ideal WiFi to Serial (or SPI) bridge?

What are some recommendations on an ideal WiFi to Serial bridge? My ideal qualities would be:

• Simple connectivity, SPI or Serial
• Reasonable fast speed, at least 1mbit/sec ideally (though probably wouldn't always need that fast)
• Inexpensive, I'm thinking under $50 • Low power -- it should use at most 100mA, if we could get it even lower like say 20 or 30ma, even better. • Built-in protocol stack -- I want it to handle the WiFi protocol, along with DHCP, TCP/IP, DNS, etc, so that all I have to do is tell it what IP/port to connect to, and then handle the data myself. • If at all possible, 5V-tolerant I/O's...to make it easy to interface to our old-school microcontrollers. So far I've found: Anyone have any experience with other possibilities? • – davidcary Feb 12 '12 at 17:13 ## 9 Answers Roving Networks offers the RN-131C and RN-131G for$45/$40 WiFi - UART. It uses 100 mA when awake, and 10 uA asleep. I'm using a related system on a project and it works quite well. The C variant is commercial temp range, the G is industrial. I think they have RS-232 as well as SPI/I2C versions as well. I'm not sure if this is the WiFly GSX you mentioned in your original question. Also, we looked at the modules from Redpine Signals. I'm not sure what their power consumption is, but the Connect-i-on series of products has the other functionality you're looking for. • Yeah the RN-131 is the same as the WiFly GSX. The Redpine modules also look interesting. – davr Apr 16 '10 at 18:21 Have you considered using a Lantronix Wiport (Wifi to Serial Module). Little Bird Electronics used to sell the Little Bird Brain Arduino Wifi Shield. Which was an Lantronix Wiport on an Arduino shield. • Looks interesting...what's the difference between Lantronix Matchport and WiPort? – davr Nov 4 '09 at 21:59 • According to this matrix: <www.lantronix.com/pdf/misc/Embedded-Module-Matrix.pdf>, it looks like there's very little difference. – Kevin Vermeer Jul 26 '10 at 15:23 Microchip/ZeroG Wireless Module I haven't used this module, but we are planning on using it. I have used the Microchip TCP/IP stack and it works pretty well. It's inexpensive and interfaces to uP via SPI bus. • I believe the ZeroG is the radio only - you still have to run the TCP/IP stack on your own processor. – mtrw Apr 16 '10 at 1:30 • That is correct, but Microchip supplies the TCP/IP stack. – mjh2007 Apr 16 '10 at 14:30 • Ok, so this is a good solution only if you are using PICs then. If you are using some other mcu, probably not a good solution? – davr Apr 16 '10 at 18:20 • Yes you are right. I think the license for their stack stays you must run it on a Microchip microprocessor. The question was tagged PIC so I thought that might be an option. – mjh2007 Apr 16 '10 at 20:44 • The WiShield and related products from AsyncLabs uses the ZeroG chipset to give WiFi to Arduino-compatible boards. – todbot Apr 28 '10 at 7:05 If you are using Arduino, the WiShield works very well with a free software stack. SPI interface between the Arduino and the WiShield, but the Arduino could turn that into serial if you want. It's a bit unclear what this project is for but I think your best bet is a premade WiFi router with OpenWRT or some similar other open-source firmware. WiFi routers have the WiFi interface and they usually have a pinheader on the board for (TTL level) serial. • I didn't outline a specific project because I wanted to get all types of suggestions. This is an interesting one I hadn't thought of, hacking a wifi router itself. However it's not quite what I want for my specific project, since it is much larger and uses more power than something designed for mobile applications. To be fair, a router itself has much more processing power than the two options I listed. – davr Nov 2 '09 at 17:55 • WR703 is tiny and very low-power, very popular, and this sort of project has already been done with them: dangerousprototypes.com/2013/01/04/tl-wr703n-and-usbip-tutorial – John U Jan 8 '13 at 17:07 I've used the Lantronix XPort Pro (Ethernet) before...very straightforward, and excellent support staff. If you use the Matchport, call them! In my research, I also found the Digi Connect Wi Me, but I did not end up selecting it. It does have a smaller form factor than either of the above, and lower power consumption than the Matchport, but the price was much too high. ($130) Also, it runs on an ARM chip, rather than x86 like the Matchport, so receive/idle/sleep power requirements are lower.

Transmit power is similar for both devices. It's dictated by the antenna power requirements. While you can easily get average current that low (Short, high-density packets and long sleep times), you won't find one that will transmit at the required power with less than a couple hundred mA. Virtually all of the 650/750mA of current that the Matchport and Wi Me draw during transmit is due to the amplification of the antenna.

The WiFly GSX is an option that I didn't find. Low power due to ceramic antenna, and designed for battery powered applications. Good and bad things stick out to me about this chip. Good: It has general purpose digital I/O, analog inputs, and the firmware is upgradeable wirelessly, which are awesome features. Bad: it only includes the TCP/IP stack, not an embedded server and included OS like the others. More configuration will be required to see this module online, I think. Ask mtrw.

• Embedded server and OS is a bit overkill for many applications I think. So that could be a Pro in some cases. – davr Jul 26 '10 at 18:06
• I totally agree that some applications don't need the embedded server, but the asker was looking for "Built-in protocol stack -- I want it to handle the WiFi protocol, along with DHCP, TCP/IP, DNS, etc, so that all I have to do is tell it what IP/port to connect to, and then handle the data myself." This says embedded server to me, and that a bare TCP/IP stack will be lacking. – Kevin Vermeer Jul 27 '10 at 20:01

As pointed out by Dago, I personally use a Fon (La Fonera) or Meraki router (with OpenWRT) for connecting Wifi to a serial connection.

http://www.geocities.jp/arduino_diecimila/wifi/a2p_ddwrt_en.html

This might not be conventional thinking, but Raspberry Pi fits your requirements pretty well.

I've been trying to solve a similar problem and finally noticed that the Raspberry Pi is a pretty good Ethernet <-> {SPI, I2C, GPIO, UART} converter. It isn't expensive, you'll get it up and running in minutes, it has an expansion header, there are Linux drivers for board peripherals.

I've interfaced an MSP430 to RPi's UART without any problems, which gave me not only WiFi connectivity, but also serious processing power (think not just an ethernet interface but a web server that displays computed statistics of data gathered using the MSP430).

Sparkfun RN-XV- 40USD

Used in most hobby/Arduino projects. Has UDP, TCP and HTTP capabilities