AM1808 EVM touchscreen question

Dennis,

The AM1808 EVM should have a factory-installed jumper-wire from the PMIC's INT signal to AM1808's GPIO2[3] pin.  The interrupt would be externally signaled through the GPIO2[3] pin.  If this wire is not present, you will not be able to detect the LCD touch interrupts.

-Tommy

Thanks for the reply.

The AM1808_SOM-M1 schematic shows that PMIC INT (pin 40) goes to uP_NMIn... which goes to J17 RSVDN on the am1808 (note J17 is 'NMIn' on L138 so I presume that is where it got the name).

>>>If this wire is not present, you will not be able to detect the LCD touch interrupts.

Is this supposed to be a 'sky wire'?  Its not on schematic.(?)

BTW - I tried irq44 (gpio2) but no interrupt - even though the "TSC INT" bit comes on in register 02 (INT) of the PMIC when touched.

Dennis,

I assume by "sky wire" you mean a hand-modification?  If so, yes it is a sky wire.

The AM1808 SOM layout was based on the L138 SOM so that's why the schematic shows the interrupt going to J17.  The interrupt signal hookup error was not caught until after the boards were manufactured.

When you say that the INT bit is coming in, are you able to read (or probe) the GPIO2[3] signal to see that it is high?  If so, we probably just need to configure the GPIO module to interrupt on that pin.

-Tommy

>>>When you say that the INT bit is coming in, are you able to read (or probe) the GPIO2[3] signal to see that it is high?

I am trying to verify this signal.  So far I do not see it change but the gpio documentation is rather weak.  Here is what I am trying...

1.  I setup the PMIC via i2c to generate an interrupt on a touch.  I can read "INT" register 0x02 and observe the touch bit (0x08) come on *with a touch) and self-clear on read.

2.  I expect this bit is reflected in 0x01E26048 (IN_DATA23), bit 3. 

    a) So I clear bit3 (&= ~0x08) in 0x01E26038 (DIR23) to set the direction of pin3 to 'input'.

    b) Read 0x01E26048 and look at bit3 (0x08) in a loop with small delay

    c) Touch the screen - no change in bit 8

Obviously, there is another gpio step required to see the INT bit from the PMIC... something to do with pin multiplexing?

Note, I am NOT expecting to see an interrupt yet - just the status bit that 'could' cause an interrupt when gpio is so enabled.

TIA, Dennis

Dennis Kelly said:

2.  I expect this bit is reflected in 0x01E26048 (IN_DATA23), bit 3. 

    a) So I clear bit3 (&= ~0x08) in 0x01E26038 (DIR23) to set the direction of pin3 to 'input'.

The DIR bit needs to be SET in order for it to be input (0 = Output, 1 = Input).

Dennis Kelly said:

Obviously, there is another gpio step required to see the INT bit from the PMIC... something to do with pin multiplexing?

Yes, the PINMUX needs to be programmed to allow an external signal to drive in on the pin.  For GPIO2[3], you would program 0x01C14138 (PINMUX6) [19:16] = 0x8.

-Tommy

Tommy-

Thanks for the PINMUX code (and other correction) - however there was no change.

I disassembled the daughterboards from the mainboard looking for re-work.  I saw no rework wires on the SOM module (or LCD board).  Should a wire be visible?  (Looking for the typical thin blue wire...)

Thanks,

Dennis

Dennis,

You should see a wire connected to an unpopulated resistor pad near the PMIC (U9) at the edge of the SOM.  If not, you may want to contact Logic PD with your SOM serial number to see if they may have rev'd the PCB design to include this connection.

-Tommy