ComputerVoltageSources

I've spent some time programming I2C on an AVR ATMEGA8.  It has the 
advantage of a full I2C implementation in hardware so it's pretty easy 
to interface.  I've got it interfaced into my PSIM to convert to 9600 
baud for driving the SpeakJet.  Tomorrow I want to try and put the 
TTS256 in front of the SpeakJet and see what I can do with that.  If 
everything works out, I may upgrade my PSIM to this architecture.

I put an image of the inputs and outputs in my photo folder.  The top 
two traces are the data and clock for the I2C.  The bottom trace is 
the serial output to the SpeakJet.  The total transmission time to the 
SpeakJet is about 46 mS while the I2C is about half of that.  I'm not 
using strings so every byte to the SpeakJet requires two bytes to be 
sent via I2C (address & data).  It doesn't cut the time down that much 
but is compatible with interrupts.

To use a smaller AVR, I may try and get this running via software I2C 
in a ATTINY part.  Don't know if I feel up to that much work for the 
SpeakJet.  The ATMEGA8 is in a narrow 28 pin package.

Dave