TSC2007: I2C Interface sending NACK for basic setup command

What is the speed of I2C Bus. Can you also share schematic?

I2C speed is 100kHz. 

I2C lines SDA and SDL are pulled up to 2.8V with 2kOhm resistors. 

Attached is the touch controller's portion of the schematic. 

As noted the BU21025GUL responds with ACKs, so I'm inclined to believe the schematic is OK, unless there's something specific to the TSC2007, tho I thought these 2 chips were intended to be interchangeable...

(I think I saw somewhere - maybe Arduino forums - the user adding a "fake" read byte after they wrote to the TSC2007, but this sounds a little weird, no?)

I dont see pullup resistors on SDA and SCL Lines in the schematic. I would suggest to confirm the presense of these.

In addition please take oscilloscope shots of SDA and SCL  for the address byte to confirm if the signals are proper.

Sometimes the devce does not respond to I2C if it does not get a proper Power supply shutdown and startup sequence. Please confirm the behaviour of the VDD pin . Try a Pulldown of 10k from VDD pin to GND  and power up chip to see if you get a response to I2C

thanks for the input Sanjay, 

Yes, the SDA/SCL lines are pulled up by 2k ohm resistors, they are simply in another part of the schematic as we have a lot of unrelated stuff on this board. 

As for the VDD ramp up / ramp down - here is our ramp up/down:

Not sure I follow the requirements - is it saying we need to slow down VDD power on for the TSC2007's I2C to work or is this OK?

Working on getting scope shots of the I2C setup command. 

Can you confirm again that the command I sent in the original post above should be getting an ACK (as in, I'm not  supposed to do any dummy read or anything like that, right?)

Thanks again

and here are some scope shots of the SCA/SDL lines - ignoring the weird voltage levels - at least gives some idea on timing. Do you want it more zoomed in on some section?
This is a shot of the same setup command from the original post

I see that the initial State of the SCK Signal is Low. I think this may be a problem

Normally both SCL and SDA should be High. Then a High to Low Transition on SDA line happens while SCK is High. This is a Start . After this the SCK makes pulses ,

This is a little hard to see but this is what it's doing:

The MCU enables i2c - where it sets both SDA/SCL to high (after your red arrow), and THEN, SCL starts clocking and data is started. 

You can see both SDA and SCL high before the high-> low transition on SDA while SCL is high, and then the 0x90 (TSC2007 address) is sent over the wire. 

So you can see the 1,0,0,1 _ 0,0,0,0 

Then the TSC2007 responds with an ACK here (SDA is low on the 9th clock period).

This lines up w/ the initial post: the address 0x90 is sent over the line, and the TSC2007 ACK's it.

It only NACKs the 0xB0 sent afterwards....

just for clarity:

I'll reply back again w/ a more full capture - the above doesn't show the NACK...

OK

here is the full scope:

What is the state of SCL and SDA when the MCU is not applying I2C ? 

It should be high as per the I2C Protocol. It looks that the Clock is  Low.

Both signals are high out of reset, and after communication to every other I2C device on our board (LED controllers, etc). 

It just get's stuck low after the NACK from the TSC2007, but then if I communicate with another device via i2c, it goes back to all high after those comms are successful, as per the following screen shot from the DLA:

Understood. I shall respond furthur in a few hours today.

It looks that the device returns an acknowledge for 0x90 but not for the command byte.

Can you please change the command byte to 0x00 or 0x81 and see if you get an acknowledge?

One question: Is the Power of the TSC2007 applied at the same time as the rest of the board? 

If I change the command byte from 0x80 to 0x00, I get an ACK, so it seems that just the SETUP command is failing. 

Attached a capture showing this:

This then looks to be something more commnd specific and not realted to the I2C Protocol. I shall check the SETUP command and see if i find something.

In the meantime do not give the setup command but some other command such as 0xC6  (Measure X position) . You could try reading the X position by moving the finger  Horizontally over the touch panel.

Hi Sanjay, 

Right - reading position and everything else works fine, just not the setup command...

I'm looking for a command I can send to the TSC2007 that is basically a NOP (doesn't force an action) but let's me know the I2C is alive at startup ideally...

Do you not use the setup command as standard startup sequence? 

Or if you do - what is the actual bit sequence / do you have a DLA shot of the I2C traffic for startup / setup on a functioning board over there?

Hi Andrew,

I shall reply in a short while today

The Table indicates a N unser column for acknowledge for the setup command.

Perhaps you could try  address(Ack tsc2007)+ 10110000+(No Ack TSC2007)+Stop 

Unfortunately we do not have an EVM of the TSC2007 at the moment

I see - thanks for that note - I didn't realize that was there for a non-reserved command. 

I will try to adjust accordingly.