[SOLVED] PIC32 as a RS485 repeater.

Hi i am developing a project where i am going to need to interface a PC/104 with many sensors and actuators. I was looking on the serial bus options availables and i think using RS-485 with an proprietary protocol would be the best choice. One problem is that the RS-485 BUS need to be point-to-point, i can't build a star network. This is a problem becouse all my sensors are going to be on a star configuration where the max distance between any sensor and PC/104 will be 1.5m. My plan to solve this problem would be using a PIC32 at 80MHz as RS-485 repeaters. i would connect RS-485 or USB coming from PC/104 with one PIC32 and another other 2 PIC32 with this first one with SPI. I would have 5 new UART available ports. I would run all the ports at 20Mb/s. Is it possible to run both UARTS at 20Mb/s baud rate and SPI all toguether using DMA? How fast can i get? How big would be may delay? If not, deoes any one have any sugestion? Let me know if i wasnt enough clear. Just one more comment. I'm not using comercials RS-485 repeater becouse i need a realy compact design.

Is there any other way to build and RS-485 HUB? Would work if i build this way?

|| - RS-485 tranceiver
() - Optoisolators

RS-485 BUS -------------- TTL/CMOS level --------------RS-485 BUS
-------------------->||--------------->()---------------->||-------------------->


Thank you.