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by ci.v.ic
Thu Sep 04, 2014 10:07 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: 40Mhz GPIO read speed?
Replies: 22
Views: 40985

Re: 40Mhz GPIO read speed?

A bit processing is possible between I/O commands without lowering the frequency, seems that the I/O commands block the execution until the pin can be changed. But that's just an observation.
by ci.v.ic
Thu Sep 04, 2014 9:14 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: 40Mhz GPIO read speed?
Replies: 22
Views: 40985

Re: 40Mhz GPIO read speed?

is 25Mhz the frequency you get from toggle on/off? if yes than you got 50M change per second. Also you assembly will have been faster if you didn't recalculate the bit all the time. Hi Daniel, according to the photo of the oscilloscope it was indeed 25 MHz. And you are right, my code is not optimal...
by ci.v.ic
Fri Aug 29, 2014 1:16 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: 40Mhz GPIO read speed?
Replies: 22
Views: 40985

Re: 40Mhz GPIO read speed?

I'm sorry it was only bit banging (toggling pins). There is second memory interface but I'm trying to find a documentation about that interface for months. Probably it is only for sd cards but maybe it is really for a second memory chip.
by ci.v.ic
Fri Aug 29, 2014 12:46 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: 40Mhz GPIO read speed?
Replies: 22
Views: 40985

Re: 40Mhz GPIO read speed?

I was able to read and write a 5V SRAM with 25 MHz max. I used assembler code to maximize the bit banging method, however, 40 MHz seems not to be possible. Details here: http://d-fence.sytes.net/raspberry-pis-gpio-speed/
by ci.v.ic
Wed Aug 20, 2014 11:40 pm
Forum: General discussion
Topic: Adding RAM to Pi
Replies: 52
Views: 88901

Re: Adding RAM to Pi

I also would be really interested in informations about this memory interface for a project at our university. I'm searching for months but nobody can help me, e.g. Broadcom even does not answer. However, this is the most strange memory interface I've ever saw, with more data than address lines. I h...

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