25 lines
1.1 KiB
Plaintext
25 lines
1.1 KiB
Plaintext
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See the top level README for information on where to find the
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schematic and programmers reference manual for the ARM processor
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on the raspberry pi. Also find information on how to load and run
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these programs.
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So when surfing through the linux source for the raspberry pi I found
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some watchdog timer registers that dont appear to be in the datasheet.
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So I played with the registers a bit and it appears that from reset
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and/or using the settings as configured in this code, the watchdog
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timer is a divide by 4000 of the system timer, so 250,000,000/4000 =
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62500 Hz.
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Based on assumptions from the linux code the biggest timer is 0xFFFFF
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which is 16.8 seconds. If you do not reprogram the timer and let it
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run out, then it resets the chip, down to re-reading the sd card and
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bringing the ARM up using kernel.img.
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This example simply uses the watchdog timer to time the led state
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changes. Because it reprograms the watchdog timer with a new time
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the timer does not timeout and reset the chip. Comment out or remove
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the break in the loop and it will timeout and reset the chip.
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