Light Buddy Firmware (part 7)

Back to the LP5569.  I have been working on this on and off for several days and finding very little info on this.  Dont know if it will help the Maker community, but I will publishing the initialization routines, at a minimum, once I am done.

I started by writing a small set of routines to interface to the LP5569.  Then I started writing an initialization routine, followed by a status routine.  To start the testing I did some very limited writes and reads.  However everything that came back was all zeroes.  Because of the way my I2C routines are structured, I know that LP5569 is ACKing the request, otherwise the routine would hang. (Great for testing, but bad news in production.)  With out a USBEEE to decode the I2C messages, I had to resort to doing the decoding the old fashioned way, with a scope.  The scope confirmed that I indeed was getting back zeroes and that all portions of the I2C protocol was working.

I go back to the data sheet to see what I am missing.  What I was trying to do was map the LEDs to the one of the 3 Control Engines in the LP5569.  While the data sheet is not bad, it does suffer from assumption.  It is obvious that the writer was very familiar with the LP5569 and assumed the reader was almost as knowledgeable.  I had missed in the register definition section that the Engine Mapping registers were READ ONLY from I2C.  So initializing these is a waste of time.  Once I got past this the writing and read back worked much better.

The next problem was setting the PWM state for each of the nine LEDs.  Again writing did not seem to have an effect.  It always return all zeroes.  My first thought is that this was a read only register too.  But it is clearly marked R/W.  So I did a search on the data sheet for all mentions of PWM. In section 8.3..1.2.1 it says
  
"This register cannot be written when the program execution engine is active,which could result in undesirable behavior. Care should be taken to update these registers only when the program execution engine is idle."

Looked at all of the engine control registers and read them back.   All were in the default state, which is off.  The register definitions never mention idle as an Engine state, so this was causing some consternation on my part.

Continuing the search, I found in the section on LED fault detection a sequence listed.  In this sequence, you need to first enable the LP5569 through the CONTROL register (called the CONFIG register in the register summary table) and then set the PWM setting to 100%.  So I switched the order and now I can control the PWM percentage.  A few other setup registers were programed and checked, with success.  Now it is off to seeing if I can actually control the LEDs.