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 Robotics / NXT / NXT Firmware Hacking / 60
59  |  61
Subject: 
Re: pbLua PCF8574 SOLVED !
Newsgroups: 
lugnet.robotics.nxt, lugnet.robotics.nxt.nxthacking
Date: 
Mon, 21 May 2007 21:27:33 GMT
Viewed: 
112 times
  
In lugnet.robotics.nxt, <dickswan@sbcglobal.net> wrote:

Hi,
or was it a quirk at my brain to address the i2c-read-address and
hope to receive usefull data ?

Currently it works for me when using allways the i2c-write
address...


This is the excepted behavior. When you want to read from I2C device,
the NXT firmware first sends a write message to load the internal index
"pointer" for the I2C device and then sends a read message that will
read the requested number of bytes. Usually I2C device auto-increment
the internal index pointer whenever a message is r/w multiple bytes.

Hi Dick,
your answer solves my knot :D
It's a NXT specific behaviour and all alternatives NXT-OSes which uses original
Lego-Source-Lowlevel routines have this feature ?

Thanks for your answer
Bye
Christian



Message has 1 Reply:
  Re: pbLua PCF8574 SOLVED !
 
(...) Let me say thanks to Dick as well. I think that the NXT firmware does what's called a repeat start in the I2C definition... Here's the part in the I2C spec that is required: (URL) And with pictures: (URL) Hope this helps... Ralph (18 years ago, 21-May-07, to lugnet.robotics.nxt, lugnet.robotics.nxt.nxthacking)

Message is in Reply To:
  RE: pbLua PCF8574 SOLVED ?
 
(...) This is the excepted behavior. When you want to read from I2C device, the NXT firmware first sends a write message to load the internal index "pointer" for the I2C device and then sends a read message that will read the requested number of (...) (18 years ago, 21-May-07, to lugnet.robotics.nxt, lugnet.robotics.nxt.nxthacking)

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