There are updated i.MX27 SOM-LV schematics that will be posted to the web site as soon as they are approved by the design team. They show the proper GPIO connections for the status LEDs.

J1- 218 - Status 0
J1- 216 - Status 1

New i.MX27 Schematics are posted

I've been trying to get the Linux touchscreen driver to work on the i.MX27 SOM-LV and needed to know which pin the MC13783 interrupt is on.

The latest schematics (Rev 4) show the interrupt from the MC13783 connected to pin D24 of the mx27, while the previous schematic (Rev 2.4) shows it connected to pin E17.

I have two boards that behave as if they are midway between these two schematic revisions. The GPIO pins for the leds work (which would imply Rev 4), but the interrupt from the MC13783 is actually connected to pin E17 (which would imply Rev 2.4). I determined the interrupt pin location experimentally by watching all the GPIO pin states during a touch, and in fact the driver works if I use pin E17 as the interrupt.

The boards have a sticker on one of the memories that says "1008521 Rev 2", another one that says "Model Number: MIMX27CSOMCR-A", and the pcb fab has "1008514 Rev A" in copper on the backside.

How do I tell which schematic is correct for the Revision of boards that I have? And if it is in between Rev 2.4 and Rev 4 where can I get a copy?

Dave,

It looks like there was a Rev. 3 of the schematic used on a small second run of Pilot boards. It had the GPIO fix - so you are correct in your analysis.

I would recommend you design your baseboard to the Rev 4 schematic as that is the current design.
Thanks

Richard

Dave:

My board has all the same markings as yours. However, configuring to use pad E17 does not get me the PMIC interrupt (neither does using the signal from the rev 4 schematic). How did you manage to probe the GPIO signals? Via some software method in kernel space? The signal E17 is connected only between the PMIC and the i.MX27, i.e., it doesn't go to the breakout board. The ts_mxc thread polls the touchscreen every 20 ms, attempting to do an ADC conversion. Since I don't get the interrupt, the thread just waits forever on the first poll.

Any ideas or further insight?

-john

Ok, the touchscreen for my ZoomLite now works under Linux using pad E17 as the PMIC interrupt source. Schematic 2.4 is closer to right than 4.0 for my i.MX27 SOM board. The reason I couldn't get it to work after I switched from pad D24 to E17 was that I derived the interrupt pin number using the wrong port (port 'F 'instead of port 'E'). It's easy to make this mistake because the Freescale macros to encode a pin use port numbers instead of letters (and yeah, I can't count).

This took days to figure out. Be wary of automatically replacing your schematics with the latest ones. Somewhere there should be a list of board revs and what we should expect to see on the various stickers and silk screens.

Hi,
I've some problem with my ZOOM LITEKIT schematics. I need to use the F22 GPIO pin in my own hardware. I choose this pin because it's "free" on the schematics that I'm using (rev 2_4).
But when I configure the iMX27 registers so that F22 pin work as INPUT, "something" is driving the pin to 1.8V.
I thing that there is some hardware connected to the pin that is not showed in the schematics.

Indeed, my board is not the same in the schematics. I saw another differences. But I couldn't find the right schematics in LogicPD site.

Anyone knows anything about it?

Thanks.

Yuri Ribeiro.

If by F22 you mean Port F, pin 22, that signal is the output of an OR gate with 1.8V logic levels on the SOM. It is combined with another signal to create the SLOW_CS signal so it is not really available for general purpose use. This is indicated on both my rev 2.4 and 4.0 SOM schematics.

John,

Thanks for the help, but in my schematics this is not shown (rev 2.4).
I think that the OR gate that you means is the U31. The outputs of its gates is connected to the nets BOOT_nCS and FLASH_nCS.
You are right when you say that I'm using SLOW_nCS signal. But in my schematics this signal is only connect to CF_nCE signal in baseboard and the expansion board.
The CF_nCE signal is connected only to expansion board, too.

So, the SLOW_nCS signal is not connected to any device.That's because I choose it to use.
Maybe a little mistake on net names?

Thanks again.

Werner,

The important thing is to make sure the schematic you have corresponds to the board you are using. I found out (after much work!) that I have an old SOM (rev 2.4) on my board so I must use the 2.4 SOM schematics and should not have blindly started using the rev 4.0 schematic. I assumed the new schematic corrected mistakes in the old schematic - but it actually represents a new revision of the SOM.

In the version 2.4 SOM, the SLOW_nCS is solely the output of the W15 pad on the i.MX27. On the rev 4 SOM, the SLOW_nCS signal is qualified by A23 (A23_INVRT and uP_nCS5 must both be low for SLOW_nCS to be low) so that when the port pin is set low, the active low SLOW_nCS signal will be asserted whenever external A23 is also asserted.

Good luck. I hope you get it working.

-john