ADV7480 I2C NACK error

Question

Hallo, 
 We are using ADV7480 in our product as HDMI decoder. We are observing I2C NACK error while accessing registers from the following Maps 
 CP Map Address set to 0x44 HDMI RX Map Address set to 0x68 HDMI RX Repeater Map Address set to 0x64 
 However we never see any error accessing IO Map address 0xE0 CSI-TXA Map Address set to 0x94 
 The issue observed almost 50% of the time while writing to CP, HDMI RX and HDMI repeater. 
 We are currently bringing up pattern generator of ADV7480 and the register setting we use for this is 
 ":08-10 Free-run MIPI TxA CSI 4-Lane - RGB888, 1280x720p 60Hz:" from the https://www.analog.com/media/en/engineering-tools/design-tools/ADV7481ES3C-VER.3.6c.txt 
 The issue is strange as it occurs only while accessing few blocks. Please let us know what can be the possible cause of this issue. 
 Best regards, Prasad.

DharaniS · Accepted Answer

Hi, 
 Please find the initialization sequence below. I2C initialization must be carried out in the following order: 1. If required, configure any I2C writes for the desired configuration of the I2C Slave Map addresses. 2. Configure the I2C writes for the desired power-up configuration. (As mentioned in the previous comment) 
 Please ensure with below things, 
 1. Make sure the power rails are good 2. Make sure the device is out of reset and the reset goes high after both power rails are stable. 3. Make sure SDA and SCL signals are going to the right pins. 4. Verify the pull up resistors on SDA and SCL 5. Verify the SDA and SCK signals wiggle and are the right amplitude 6. Verify the start command is correct. 7. Check to see if you can access anything else tied to the I2C bus, like eeprom. Tie something to the bus to make sure the bus is working as expected. 8.Please check that the reset and power-down pins are controlled in the manner described in the datasheet "optimal power-up sequence" section. 9. Make sure SDA is really tied to the data line and SCL is really tied to the clock line. 10. Make sure the reset is tied high 11. Please try below sequence, a. Power up the chip as normal b. With a jumper wire or probe, pull the reset pin low to get a good solid hardware reset after power up. c. Try I2C transaction again. 12. Also setting Chip Reset bit is equivalent to controlling the Reset pin on the ADV7401 and will issue a full chip reset. 
 All I2C registers will be reset to their default values. After the reset sequence, the part will immediately start to acquire the incoming video signal. The optimal power-up sequence says to: 1. power-up the 3.3V supply, 2. then power-up the 1.8V supply, 3. 5ms wait, 4. then power-up the power down pin, 5. 5ms wait 6. then the reset pin. 7. wait 5ms before I2C communication. 
 Note: It is recommended to wait 5ms before any further I2C writes are performed. 
 Thanks, Dharani S)

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ADV7480 I2C NACK error