I AM CONFUSED

[vron]

how can i get a high data rate serial communication from my PIC microcontroller to a qpsk modulator
what would be the best data rate i can acheive using PIC microcontrollers
i am working to create a wireless data communication link (something like wi-fi)

pls help me out as i am too late in completion of this proj

 

[Nigel Goodwin]

A PIC is capable of 115,000 baud, which is the fastest RS232 speed.

 

[Jay.slovak]

I think he's talking about manchaster coding, which is suitable for RF transmission... And that is much slower than RS232.

 

[Nigel Goodwin]

I think he's talking about manchaster coding, which is suitable for RF transmission... And that is much slower than RS232.

It's generally about half the RS232 speed, not counting the preamble and packet overhead etc.

But I suspect he's hoping for something FAR faster?, presumably along the lines of WiFi at 54Mbs?.

 

[Jay.slovak]

Theoretical maximum, for PIC running @ 40Mhz and using Hardware USART for asynchronus mode is around 1.25Mbit, thus maximum speed for manchaster coding is 625Kbit... This does not look like Wi-Fi's 11 (or even 54 :lol: ) Mbit. Don't forget that your speed is limited by the transmiter module, and you have to implement some kind of error protection as well. If you plan on using this as "LAN", you should look for different solution... If 40Kbits are enaugh, this is a good way how to do it...

 

[vron]

thanks for ur postings NIGEL and JAY

my project is to build two wlan transceivers
ONE transceiver is connected to rs232 of pc. this transceiver has to communicate to other transceiver through a wireless link and this receiving end has to send data to rs232 of other pc

wat speed can i get between microcontroller and rs232 of the pc. and wat about the rf link between two transceivers. the modulation intended is a qpsk modulation

where can i get high data rate qpsk rf modules in india
or are there any chips which make circuit of qpsk tx-rx easier


i m in a pickle as i have to complete this in 45-50 days
you help would really get me out of this :?: :?:

 

[BF9000]

Fast 0-QPSK transceiver

Try chipcon's zigbee compliant chips. You can get samples of the CC2420 transceiver. It only has a few external components to add and will work with a PIC via SPI. The carrier is 2.4GHz and uses O-QPSK modulation. The only tricky part is mounting it as it only comes in a very small package. This is also going to require some reading on the 802.15.4 spec.

 

[BF9000]

RS232 Speed

Circuit Blocks has a very simple RS232 transceiver at www.circuitblocks.com It claims to run at up to 230Kbps. I don't think hyperterminal will support this so downlaod realterm. It is free and has a lot of nice features for debugging.

 

[Mike - K8LH]

Theoretical maximum, for PIC running @ 40Mhz and using Hardware USART for asynchronus mode is around 1.25Mbit

Actually Jay, it seems the theoretical limit for a 40-MHz PIC might actually be 2.5mbps...

Regards, Mike

 

[Mike - K8LH]

Wow, it seems you might be able to get 10-mbps out of the newer PICs with 16 bit SPBRG capability... Gosh, can that be right?

Regards, Mike

 

[Nigel Goodwin]

Wow, it seems you might be able to get 10-mbps out of the newer PICs with 16 bit SPBRG capability... Gosh, can that be right?

If you can, why would you want to?. There's very little 'RAM' (GPR's) in PIC's, so there's not much data to move about at such high speed.

 

[Jay.slovak]

Wow, thanks for new Info...
I find this usefull as serial/paralell or other converter... 10Mbits... Wow.

 

[Mike - K8LH]

If you can, why would you want to?

Nigel, I agree... I can see no practical application for anything I'm doin'... I just provided the info' in response to Jay's "maximum speed" statement earlier in the thread...

Regards, Mike