multi-processor

jones2 · ‎2004-08-01

Posted on August 02, 2004 at 07:26

multi-processor

jones2 · ‎2011-05-17

Posted on May 17, 2011 at 12:02

I'm bulding a board with four uPSD3234a.

I have some hardware questions:

1. I will connect the I2C bus to all four. Do I need extra hardware like

pull-up resistors, or just simply connect the bus and install the driver?

note: I will use one osscilator for all four.

2. can the A/D channels be connected as 4 buses, with an external connector?

so I can connect an analog device and read it from one or more processors.

3. the same question is for the USB bus.

thank you.

neil2 · ‎2011-05-17

Posted on May 17, 2011 at 12:02

Do you want to connect all four USB together at one connector? I don't think you can do this. All four devices would respond asynchronously to data sent by the host and this would result in garbage on the bus.

Do you want to connect the analog together as well, or just bring them out to 4 x 4 = 16 pins on one connector?

jones2 · ‎2011-05-17

Posted on May 17, 2011 at 12:02

About the A/D, I prefer to have 4 pins that run through all four processors.

i.e. pin1 will be connected to ACH0 of all four processors, pin2 to ach1 etc.

Then I can connect four analog devices in any order I want.

About the USB, I will use then as two GPIO, between the processors.

The best solution for me would probebly be the I2C. but I do not know if I need ust to connect I2c pins to create a I2C bus. or should I add extra components on this buss, like resistors, cap or what ever?

My play Is to use one oscillator for all four processors, I understand that it would be better for the data exchange between the processors.

but could one external oscillator (40Mhz) activate four uPSD3234a?

neil2 · ‎2011-05-17

Posted on May 17, 2011 at 12:02

Using an external 40MHz oscillator connected to all four XTAL1 pins with the XTAL2 pins open circuit should work as long as the drive requirements are met.

Not sure about the the A/D. you would probably get a much lower input impedance.

Sounds like an ambitious project.

jones2 · ‎2011-05-17

Posted on May 17, 2011 at 12:02

for DN33.

what do you mean ''XTAL2 pins open circuit''?

any special conection with XTAL1, or not connected.

jones2 · ‎2011-05-17

Posted on May 17, 2011 at 12:02

What kind of pull-up resistor the I2C bus?

jones2 · ‎2011-05-17

Posted on May 17, 2011 at 12:02

about the A/D, I will not switch between the processors.

I will select on initilization which, processors sample which

analog device, and it will not change any more.

It is just for convinience, and less wires on the PCB.

About the I2C, I see that the uPSD33xx has master/slave driver and not like the uPSD32xx that has only the master side.

[ This message was edited by: std on 31-07-2004 20:11 ]

neil2 · ‎2011-05-17

Posted on May 17, 2011 at 12:02

XTAL2 pins open circuit means don't connect them to anything.