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SPI Speed Disappointment

February 22, 2014

I went to a BUNCH of trouble to get the hardware spi working and to speed up the clock to the mhz range but the results are more than a bit disappointing.  I was still taking 1.5 sec to serve a 300 byte page – maybe 200 bytes/second!

I added in a 100 byte filler to get an incremental figure and it looked like the incremental speed was more like 500 characters/sec but that’s still poop.

The problem relates to the way the wiznet is addressed,  for each payload byte you have to send 3 protocol bytes and you have to lower and raise the slave select line for each sequence.  I took a stab at speeding up the enable/disable but it still only got me to about 800 bytes/sec.

There are a few obvious improvements left like avoiding use of strlen or limiting it but it’s not going to get me much.  I NEED AN EPIPHANY!

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