SPI and UART combined(AVR)

[Hessel B. (duckstar)]

hello dear Mikrocontroller.net users,

i am a dutch student in electronics and currently working my practical 
year/exams, my assignment is to make a controller for a Digital Sound 
Processor, for amplifier racks in Professional Audio.

in such a rack there are four DSP's who'm constantly need to be checked 
if current setting is the right one therefor i needed to create a 
network of multiple uC's the network of uC's is simply controlled with 5 
buttons and a LCD.

now come's the tricky bit(for me that is), also custom settings should 
be loaded to the DSP's this happens through the master uC's UART on to 
SPI to selected Slave in LCD menu, the slave then sends it using its 
uart to the DSP..

and this won't work. i have tested the UART it self and the SPI and both 
(seem to) work, i have pulled out my signalscoop and measured all 
variables but my output signal just isn't there.

i simply used the examplary codes from Datasheets for testing purposes 
but this didn't work either. how ever it clearly works seperatly..


the network master is an ATmega8515 the 4 slaves are ATmega8's there is 
also an SPI EEprom chip to store all the presets to. my programming 
language is Assembly.

if any of you have some working code and/or scheme's i would be helped a 
lot.