DS90UB914A-Q1: I2C NAK problem (Helped needed)

Hi Craig,

The device needs to be enabled via PDB, which should be on by default, but just in case have you verified all the switches are in the correct position (as shown in the user's guide)?

User's guide: www.ti.com/.../snlu135b.pdf

Regards,

Thanks Michael,

You were correct, I did not have PDB high (my microcontrollers data direction bit was wrong :( )
I now have my microcontroller talking to the deserializer chip via I2C. (I can read and write registers succesfully)

(NOTE: These are my own circuit boards, not the evaluation boards.)

Here is my next problem, I set PDB high, OEN high, and OSS_SEL high, after 40 usec, the PASS pin goes high,
but LOCK pin is low. (LOCK pin never goes high)

1.) Does this PASS pin mean anything at this point?

2.) My camera does not run until I setup its I2C registers (its PCLK is off), so can I forward messages over the I2C forwarder
if the LOCK pin is not high? (Note The serializer has an external 48MHz clock)

3.) Also as soon as I bring the BISTEN pin high, the PASS pin immediately goes and stays low,
when I bring BISTEN low, the PASS pin also stays low :(
Any hints?

Hi Craig,

You will need to establish LOCK before anything meaningful can happen. This is the 'handshake' between SER and DES that ensure the PLL is locked and stable and communication on both the forward (FCC) and back (BCC) channel can occur. I2C communication from the DES side to the SER side will happen over the BCC.

The PASS pin won't have much meaning until LOCK is established.

Can you please read registers 0x02,0x03, and 0x1C ?

Regards,

REGISTER 0x02 = 0x00

REGISTER 0x03 = 0xE9

REGISTER 0X1C = 0X00

Hi Craig,

Register 0x1C is the general status register and it's showing you still don't have a lock.

Are you adhering to the power up sequencing described in section 9.1.2 of the datasheet for both the serializer (913) and deserializer (914)?

If the FPD-Link system is not initialized in the correct sequence, the DS90UB914A-Q1 may need to be reset with signal present at the input to the Deserializer to optimize the link:
1. Toggle the PDB power down reset pin, or:
2. Perform Digital Reset 1 writing register 0x01[1] = 1

If you do have a 913 EVM it may be worth connecting that to your board that has the 914 and see if you can establish lock with that.

Regards,

Hi Michael,

Thanks for your help.

  My serializer board is designed directly from the camera example board schematics from TI, and the deserializer is also designed based on EVM schematics.

So I believe the power up sequence is correct, My microcontroller also always pulses the PDB line on startup.

Here is a few more questions I have:

1.)  If the camera is not running on startup, it will not produce a PCLK Input to the serializer. If PCLK is not running, will a LOCK ever be achieved?

2.) I never performed proper calculations on my microstrip trace from the coax connector to the deserializer chip. after performing these calculations,
it looks like the impedance of the trace is 75 ohms. Will this prevent lock? (my traces are maybe 1.5" long at most.)

3.) I did a previous design with my camera connected directly to a PIC32MZ processor. In order to make this design work, I had to lower
the PCLK output of the camera to around 15MHz. I am using a coax, which I see has a minimum PCLK of 25 MHz.  Am I totally out of luck?
or can I use the twisted pair? Will the 913 and 914 work at 15MHz? If not are there other options?

Hi Craig,

1.) No, you won't get lock.

2.) Mismatched impedance will also prevent lock. I think there is a tolerance usually of around 10-15% of 50ohms but 75ohms is well above even that.

3.) Unfortunately, the minimum PCLK is 25MHz, you may get away with ~23-24MHz but performance wouldn't be guaranteed. This is necessary to support the forward channel data rates.

Regards,

1.) If Camera is not outputting PCLK on startup, then I can't get lock, if I don't have lock,
then I can't send I2C information to startup my camera?
Is this correct?

2.) If I don't have lock, will the GPIO[x] pins still get transmitted?
(My camera reset pin is on this GPIO[0], and the camera power down pin is on GPIO[1])
If the above is true, then I guess I don't have any way to startup my cameras PCLK, and
therefore my boards will not work :(