propeller with MAX6974 led chip

jo_elektro

Hello everybody,

I'm actually a PIC person (altough i started of with the stamp ) but in a recent project i've been working on, the PIC has let me down and i'm now looking into the propeller chip with it's wopping 160 MIPS.
How ever, I need some senior advise on how to go about, for this 8 cog thing is a complete different way of handeling than I'm used to.

It melts down to this:
The MAX6974 is a 24 pwm RGB led driver chip with a kind of SPI bus, running on a constant clock in orde to be keept alive. On this clock stream, data is sent to the chip regarding the individual color intensitity and others. A job any MCU could do.
But.... in order to have a descent frame rate (combined with an insane cascading technique) the constant clock must run on about 15 to 20 Mhz.
With a pic running on 65 MHz i can only get up to about 700 KHz of data stream (i can go faster but then i'm unable to clock the data along)
With the propeller it seems that in theory this should be possible but I suspect that I wil have to distribute this job onto a number of cog's.
I was thinking of using one cog to generate the ~15 Mhz clock with it's internal counter module and control four cogs for the data, spreading the load bitwise over each.

As I said, i'm used to the PIC and the possiblitys of the propeller and it's parallel approach is still seeping slowly into my brain.
Any input on how to approach this would be highly appreciated.


grtz,

Jonathan

PS. I got myself the propeller starter kit and have been dabbeling with the tutorials and pre made spin programs in the library.

Leon

I don't know of any PICs that run at 65 MHz! 40 MIPS is the maximum for some of the 16-bit PICs, the 8-bit chips are a lot slower. Do you mean 16 MHz?

Leon

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jo_elektro

Indeed, 16 Mhz and trough a 4xPLL = 64 Mhz (and not 65, my bad).
Currently using the 18F26k20 giving max 16 MIPS.
I had a look at the 32MX series which run 80 Mhz (1,56 DMIPS/MHZ ) but they have so much peripherals onboard which are of no use to me and have little in common with the "lower" series that I rather go for the propeller.

Post Edited (jo_elektro) : 6/2/2009 12:54:13 PM GMT

Timmoore

Take a look in obex and search this forum for the tlc5940. This is a similar led driver with what sounds a similar type of clock. One driver I know of uses 2 cogs: one for the clock and one for loading data. Another driver I know of uses 1 cog: it uses counters for the clock and code for the data loading (I wrote this version). You can probably get most of the ideas from one of those.
I just took a quick look at my driver and it looks like I am running the counters at system clock/4 i.e. 20MHz.

jo_elektro

Thanks a lot, Timmoore.
I've found the spin objects and will disect them in the next few days.

Got a feeling that the propeller will make me go "Wow" :P