[beagleboard] BeagleBone hardware change request

Pad D13 is already accessible on the expansion header via the CLKOUT2 pin . Make sure you look at the latest schematic.
Pad B12 is already accessible on the expansion header via the GPIO0_7 pin . Make sure you look at the latest schematic.

PAD H18 is not accessible and we have no extra pins for it. We may be able to piggy back like we did above, but this change would not happen for a long time until the next revision, assuming I can make it work without blowing up the processor in the process.

I will take the last one under advicement. I really do not want to start down this path of making changes unless there is a BIG reason to do it for a LOT of people and there is clear benfit to doing it.



Thanks, I do indeed have an old schematic. The ones on the BeagleBone resources page are rev A3. I just found the A5 ones at

Are the A6 available?

A6 is availlable. Go to my WIKI page.




Does this mean that with the current design I cannot use mcasp1 port as a normal I2S audio input/output ?

As I understand I need mcasp1_axr3, mcasp1_axr2, mcasp1_fsx, mcasp1_aclkx but on the latest SRM I don’t see them. I want to implement a cell phone cape and wanted to use mcasp1 for audio instead of mcasp0 to able to stack it with the audio cape.

Also on the last SRM on table for P9.41 clkout2 shows pad D14 not D13 ?¿?

Thanks in advance

Look at table 2-55 in the AM335x datasheet. That gives you the pin numbers onto which pins the MCASP1 signals are located.

Looking at the first signal in your list:

mcasp1_axr3…H18 (RMII_REFCLK for the Ethernet,does not go to the expansion header) L15 (RMII_RXDA for the Ethernet, does not go to the expansion header)

As you can see, this signal is not available on the expansion header for you to use. That is why you cannot find them on the expansion header tables anywhere. So, you cannot use McASP1.

There does appear to be an error on Table 11. I will fix that on the next release.


Thanks a lot Gerald !

Dear Gerald,

Pad D13 is tied to CLKOUT2 but on SRM says pad D14

The schematic says D14 is connected to CLKOUT2. That is on page 6 of the schematic.
The schematic says D13 is connected to GPIO3_20. That is on page 4 of the schematic.
The datasheet says that D14 is CLKOUT2.
The datasheet says D13 is GPIO3_20.
Table 11 of the latest SRM (A6.0.1) says D14 is CLKOUT2 and connected to expansion header P9 pin 41.
GPIO3_20 is connected to R221. The other side of R221 is connected to…D14.

So, if you look at the schematic, BOTH D13 and D14 are connected to P9 pin 41. That is the way I designed it. And that is the way it is. This change allowed us to get additional signals out to the expansion header. It is up to SW to set and use the pins as it sees fit, assuming that it only uses one at a time, please.

Please do not be afraid of reading the schematic. Do not just rely on what the SRM says. Check the schematic. I will in the next release of the SRM add a detailed description of what is going on here, how it should work, such that those that choose not to read the schematic will be covered.

Sorry for any confusion that this may have cause.