[Bicycle LED POV - 397] BicycLED POV

[Casainho]

Finally I was able to do JTAG debug on AT91SAM7S128! Thanks to
different versions of OpenOCD, the last scripts didn't work with
recent version I am using, 0.4.0.

My task was to make code for drive the HC595 LED drivers using SSC
peripheral, since AT91SAM7Sxxx just have one SPI and it will be used
instead for the uSDCard(or SPI DataFlash) using DMA.

I was able to put SSC working, with a clock of about 0.75MHz just as I
wanted. The clock signal can be seen on first image.

Other images are the clock signal and SSC TD pin, working here as MOSI.

It's late now, on next days I want to connect that signals to HC595
and drive some LED, to test the current schematic. I am using Olimex
SAM7-H256 board (with AT91SAM7S256).

--
Cumprimentos,
Jorge Pinto

--
You received this message because you are subscribed to the Google Groups "Bicycle LED POV" group.
To post to this group, send email to bicycl...@googlegroups.com.
To unsubscribe from this group, send email to bicycleledpo...@googlegroups.com.
For more options, visit this group at http://groups.google.com/group/bicycleledpov?hl=en.

[Casainho]

The current firmware on SVN trunk have the drivers for SCC working as
SPI, for communicate with the "74HC595 LED drivers".

It also have the PIT working, generating an interrupt every 1ms, and
that make works the "delay(ms)" function.

Me and Francisco, we were looking at oscilloscope and testing the
"74HC595 LED drivers". These IC is not perfect to work on this
application and we saw big losses on internal output resistance. I am
sending a picture of oscilloscope were we can see the voltage output
from 74HC595 is 2.88V while it should be 3.3V -- it means a loss of
power important if later we want to use another LED, like blue ones,
were we will need an higher LED Vf.

I made that test with 74HC595 sourcing the current. Later I made the
same test but this time with 74HC595 sinking current. The schematic on
SVN trunk is final. We are now starting with PCB design and buying the
components for 3 prototypes.

Note: The 5mm LED on picture are the ones from LEDShoppe*. They are
not good LED but they are cheap and may be enough for this
application.
* http://www.ledshoppe.com/Product/led/LE1018.htm