Using I2C with FullSpeed USB

[mister_e]

how many byte do you read at the time?

still working with a single byte at the time? if so, just do loop and insert a USBSERVICE inside

As now i didn't use I2CREAD/WRITE with USB ones so...The MSSP is also suggest by me.

Charles.. i'm with you

[Demon]

Steve, the MCP23016 has 16 bytes and I'm using at least 13 of them.

Robert

[mister_e]

miip 16 bits, 2 bytes. i don't remind how to access to them.. since too much time i don't use them can you refresh my single workable brain cell on this friday before i left home to night club

[Demon]

D'uh, yeah, bits.

I just use I2CREAD for a WORD and get all 16 bits in one shot.

I checked the MicroChip site and they have the MCP23S17 which goes at a maximum of 10MHz in SPI mode. I don't think that's worth the effort to even try.

But I did get another idea; using a 16F628 to read the MCP23016, sets 4 output pins to a binary value (I just need the number of the 1st active pin) and then sets a READY pin. The 18F4550 works on USB until the READY pin is set and then reads the 4 input pins. TADAA!!! Super fast 16 bit parallel exchange between 2 mcus.

I just don't know how the 18F4550 can reset the READY pin though. I never got a full grasp of that concept.

Robert


EDIT: Reviewing my own thread from a while ago:
http://www.picbasic.co.uk/forum/show...ight=busy+line

[mister_e]

mmm, that make me think of few things to try on sunday... i'l do some test with the 4550 and I2C... Anyways i guess that one project i have in head will probably need at least one I2C external device... so i'll hae to mess with I2CREAD/WRITE and/or MSSP anyway.

Your point is valid but need extra hardware... sure workable, but it have to be done without it. The MSSP is the one i mostely suspect workable. SPI is faster than I2C... but MSSP i2C is more fast than PBP I2CREAD/WRITE

mmm...

[Demon]

Steve, I don't have much choice. The SPP feature on the 18F4550 has only 8 bits, I need at least 13.

I wonder if I can do this with discrete components instead of using the MCP23016 and 16F628 to generate a 4 bit combination. I have 13 momentary push-buttons that I have to get to the 18F4550 as fast as possible.

I'm sure there's another way. I'll ask on an electronics forum and see what the gurus there come up with.

Robert

[mister_e]

Sure it have 8 bits... 2 successive read .. well something like stated somewhere in the MCP datasheet. It must exist a quick drwaing of it somewhere in.

if you really want to add stuff, 4 choice spring to mind

use a bigger PIC than the 16F28, then just read the i/o, send it to the 4550 via USART.

Use a keypad decoder like 74c922

Use a single (or more) A/D pin of the 4550 with a multi-step voltage divider... yisssh

Find a multiplexer... time is short now, but it have to exist, i had the 4067 idea... but i'm not sure... i must forget something on this chip.. what? i don't know.