data transfer between 4 PIC18f4550 using their usb port.

[drbizzarow]

hi frndzzz,

i am trying to do some fast data communication project... serial UART of pic not fulfilling my requirement... so it possible i can send data from one controller to other controller using their USB port?????

thx

 

[betwixt]

Not with 18F4550s, their USB port only works as a client, in other words it has to be connected to a host to work. You could try SPI, it should be possible to work much faster than UART serial can manage.

Brian.

 

[drbizzarow]

i want to fetch RGB led matrix frames from SPI RAM and scan it @ 60hz.
i have decided that one controller fetch data from SPI RAM and share it to other controllers through its USB port they will do scanning and PWM stuff. this will save complex h/w like dual port ram etc.

any suggestion regrading this ???

 

[betwixt]

If you want to use USB you will have to use one of the PIC24 devices with 'on the go' USB hosting but I doubt it would make your system any faster.

If your SPI RAM holds data for several controllers, why not let them share an SPI bus and use addressing or hardware enabling to select the appropriate device. SPI can transfer much faster than USB and is far easier to implement. The PICs could take turns to their block of data from the RAM.

Brian.

 

[embpic]

The controller you are using which can be used as slave for USB protocol. In USB protocol ther is mainly only one Host so for that u will need to use controler support USB host. you can go with other protocol like I2C, SPI and also with UART.

 

[drbizzarow]

If you want to use USB you will have to use one of the PIC24 devices with 'on the go' USB hosting but I doubt it would make your system any faster.

If your SPI RAM holds data for several controllers, why not let them share an SPI bus and use addressing or hardware enabling to select the appropriate device. SPI can transfer much faster than USB and is far easier to implement. The PICs could take turns to their block of data from the RAM.

Brian.

thx Brian,
Pls conferm PIC18f4550 have 1K dual port ram ??? if yes can i use it with SPI in DMA mode .... i mean my SPI port get data and put it on shared RAM and in main loop i do scan stuff.??? (i am not sure about this idea just getting your point off view)