BeagleBone PRU Pins

GoogleGroups
1

Hi Gerald,

I happened across this handy spreadsheet today, which maps out the BeagleBone’s Expansion Header PRU GPIO:

https://docs.google.com/spreadsheet/ccc?key=0As0aJokrBccAdGkxeHkyYW1qRHNQdm5yZDhPQlRNR2c#gid=0

Am I correct in assuming that 28 pins on the BeagleBone’s expansion headers can be used for GPIO output (controlling servos, toggling LEDs etc)?

Is the PRU able to control 28 pins concurrently, and what would the performance impact be for attempting that with all 28 pins?

2

The PRU pins are mostly scattered and as such have no real value. The most that you can use that are controlled in one group is 8. That was the reason I added two additional pins on top of other pins was to get a grouping of 8. The other pins are pretty much useless as PRU pins. Most of the pins on th eexapnsion header, as documented in the System Reference Manual, can be a GPIO for controlling anything such as an input or an output. GPIO pins do not connect to a PRU.

Gerald

3

>From: Gerald Coley [gerald@beagleboard.org]
>Sent: Thursday, January 10, 2013 7:14 PM
>To: Gregory Perry
>Cc: beagleboard@googlegroups.com
>Subject: Re: BeagleBone PRU Pins

The PRU pins are mostly scattered and as such have no real value. The most that you can use that are >controlled in one group is 8. That was the reason I added two additional pins on top of other pins was to get >a grouping of 8. The other pins are pretty much useless as PRU pins. Most of the pins on th eexapnsion >header, as documented in the System Reference Manual, can be a GPIO for controlling anything such as an >input or an output. GPIO pins do not connect to a PRU.

Gerald

So that means 16 total pins that can be controlled concurrently via the two PRUs? Or is it 8 total across both?

4

If you want to collect parallel data in contiguous order, you are limited to 8. If you have no issue collecting data in a non contiguous pattern and then regrouping it, then go for it. If you are only using one or two pins, then you should have many places to choose from.

That is what I meant by my statement.

Gerald

5

If I am reading all the PRU pin documentation correctly, the only available PRU Output Pins on a BBB (without disabling the eMMC or HDMI) are the following:
PRU0: P9_42, P9_27, P9_41, P9_25, P8_12, P8_11
PRU1: P9_26
Correct?

Thanks

6

You can read or write in any other pin with pru addressing this via memory position, is slower than direct access, but in most applications not matters, this method off access not interfere in speed off principal processor…

Maycon