PIC as a Wireless LAN node

[Oznog]

What would be the minimum hardware required for some sort of microcontroller to act as a wireless node, maybe need to do 128 bit WEP? Hook into a wireless laptop card? Is it practical at all?

 

[Nigel Goodwin]

What would be the minimum hardware required for some sort of microcontroller to act as a wireless node, maybe need to do 128 bit WEP? Hook into a wireless laptop card? Is it practical at all?

I wouldn't have thought so?.

A PIC doesn't have enough RAM to handle the amounts of data required, never mind the speed you need!.

 

[motion]

What would be the minimum hardware required for some sort of microcontroller to act as a wireless node, maybe need to do 128 bit WEP? Hook into a wireless laptop card? Is it practical at all?

Most available wireless chipsets have built-in processors that are far more powerful than the PIC. Many of them use an ARM based processor. This somewhat relieves the host of most of the heavy lifting. However, they interface via PCI, mini PCI, cardbus 32 or even USB (needs USB host).

The best chance to interface a PIC to these chipsets is via SDIO or async serial interface. Checkout the ff. link:

https://www.lantronix.com/device-networking/embedded-device-servers/wiport.html

 

[pkshima]

The footprint of the TCP/IP stack would be too big to fit in any PICs flash I guess. Let alone the memory required for the crypto algorithms for WEP etc.

Atleast I wouldnt be looking at a laptop card to begin with cause its meant for attaching to PCI, PCMCIA etc bus and PIC doesnt have that. Maybe try searching for 802.11 modules ?

for the right mcu, maybe Zilog ?

 

[Oznog]

Well I'd want to avoid really expensive ready-made devices. Hacking a cheap wireless PCMCIA card would be nice, but of course I'm skeptical of how realistic this scheme may be.

These guys made a really, really small "uIP" implementation that looks like it'll fit within the RAM space of the largest PICs (up to 3968 bytes):
https://www.sics.se/~adam/uip/

But if a wireless card is used, then is that hardware implementing the stack and WEP functions? That would mean the PIC device would just need to be a PCMCIA bus controller. I take it there's no slick "back door" SPI bus, like an SD flash RAM card has, on a wireless card?

 

[MikeHibbett]

I'm building a wireless node using a PIC and a standard compact-flash WIFI card. It's a PIC18F452.

There are several very useful TCP/IP implementations available for the PIC; I'm using the Microchip TCP/IP stack ( about 30KB ) which includes and SNMP agent. other great stacks are

https://savannah.nongnu.org/projects/lwip/

and also

https://www.sics.se/~adam/uip/

Mike.

 

[Oznog]

I'm building a wireless node using a PIC and a standard compact-flash WIFI card.

OK, yeah that's kinda what I'm thinking of, like this stuff:
**broken link removed**

But that's still electrically identical to a PCMCIA interface, right? How do you get a PIC18F452 interfaced into it?

 

[MikeHibbett]

Drop me an email and I'll send you the circuit diagram and PCB layout. I've had a could of boards made but haven't written the code yet.

Regards,

Mike


mikehibbett [@] oceanfree [dot] net

 

[Oznog]

BTW, PIC18F452 is no longer recommended for new designs. The replacement is the PIC18F4520.

Man, that thing had a SHORT product cycle. The 4520 is the same cost but a bit better if I recall correctly.

 

[MikeHibbett]

Yes, I know the part is no longer made, but there are still plenty in the supply chain. I'm using the low voltage variant, which I can get in a '452 but not in any other series.

Mike.