Hello Folks,This would address both electronics and embedded engineers. Is there a method to coax a regular built-in WLAN port on a laptop (or a WLAN card) into piping out a simple and slow on/off data stream? Without protocols and all that, and without waiting for any receive packets.The reason behind this idea: Assume you have a small uC based product. Every once in a while it needs to be updated with new firmware. The usual scenario is to provide a USB connection or an infrared port. Both are cumbersome. USB adds a lot of cost to the target device and the cable gets in the way (oh drat, forgot to pack the cable...). Infrared is tough because many laptops simply don't have it. However, nearly all of them have built-in wireless these days.The scenario I imagine is this:a. The target device is equipped with a simple and not very sensitive receiver and AM detector for 2.45GHz ISM (WLAN range). This runs into a comparator port of the uC. Much simpler than Bluetooth and all that, plus lots of laptops don't have Bluetooth.b. The user receives one executable file containing the new firmware, code to initialize the WLAN port and code to run that port in a simple (but legal) AM on/off mode. This executable would now be started.c. The user is instructed to press a magic button combination which sets the target device into re-flash mode, upon which it waits for a data stream from the WLAN card.d. The user must place the target device within a couple of feet of the WLAN equipped laptop until a LED flashes, indicating that it has detected the presence of a sufficiently strong pulsed carrier somewhere around 2.45GHz.e. A serial on/off data stream is constantly pouring out of the WLAN port of the PC. A bootloader in the target device looks for a passcode and when it finds that it loads the data stream that follows.f. The target device stops at an end-of-file token, does sufficient integrity checking on what it has received and then leaves re-flash mode. It's now ready to use...

If you want to stay within the normal WLAN protocols, it's possible totell the WLAN card to set up an IBSS or Ad-Hoc network (it can do thatwithout other WLAN cards present). Then you can send broadcast packets,and the WLAN card will forward them on the 2.45 GHz band. Broadcastpackets won't need any replies. Be prepared that the OS network stackwill also send out broadcast packets over the same network interface bydefault.For closer control you need access to the firmware of the device, whichisn't going to be available typically. In a hypothetical situationwhere you had access to such firmware, you may be able to turn thetransmitter on and off much quicker (although such behaviour may falloutside the regulatory limits)Do you intend to send the entire data stream as AM on/off signals ? Inthat case, the IBSS method won't be very practical, since each packetcontains considerable overhead. A few thousand packets/second would bethe upper limit. If that's enough, you could conceivable send...

WLAN card to generate pulsed RF?

Oct 26, 2006 82 Replies

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Terry Given 19 years ago

que? NFC?!

Cheers Terry

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Wim Ton 19 years ago

NFC (Near Field Communication) is a reuse of the protocols for contactless smartcards. It is ment for distances of some 10 cm at reasonable datarates. It uses load modulation or AM on a 13.56 MHz carrier (licence free ISM band)

Wim.

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Terry Given 19 years ago

Danke.

Cheers Terry

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