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car_computer > 2002 > usb_dock

document updated 22 years ago, on Nov 10, 2003

Requirements

Multiple PICs (eg. at least 8) attached to a network, all addressable from a single connection
Use 12 volt lines for noise immunity in a car environment
Have the easiest interface to the rest of the perhipheral network as possible.

PIC network protocol

RS232 intertangled with a DIY protocol, likely with slaves that don't talk until the master asks them to speak
Built-in I²C as master & slave (I2C doesn't allow slaves to initiate a conversation. Multiple masters are possible, but it's a lot more complicated)
Built-in SPI as master & slave

PIC network external interface

There are several ways to do this. Probably the cheapest way is to build an I2C/SPI⇔parallel/serial converter from a PIC, then tack on a serial/parallel⇔USB converter that's known to work under linux. (note that the 16F877 and 16F876 have both a UART and a SPI/I2C interface, so that would be required if we went the serial route)