Can't communicate with LTC2497 ADC chip using I2C

Projects
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Hi,

I hope you are all doing well in this new year.

I have designed my first PCB using KiCad, and it has been produced by JLCPCB.

I use FSR sensors to measure pressure. The analog signals are then digitized using an LTC2497 16-channel 16-bit ADC chip. The PCB is connected to a microcontroller using an I2C interface.

I am using an Arduino Uno, but I cannot connect to the LTC2497.

I used this I2C scanner script from Adafruit to detect the I2C addresses, and it found an I2C device at 0x01, but I cannot communicate with it. The I2C address of the chip should be 0x14 (the three address pins are connected to ground, see datasheet p.17).

The PCB LED works, and the voltage between the ground and power pins is 3.1 V.

The first time I used the PCB, the voltage at the SCL and SDA pins was around 3.1 V. Now the voltage stays low, around 0.2 V for these two pins. The LTC2597 chip is quite hot. I do not have an oscilloscope to debug the I2C connection further.

I have ordered five PCBs from JLCPCB and the same issue has occurred with a second one. I am wondering if there is an error in the schematic or the routing. I’m hesitant to test the remaining PCBs as I don’t want to risk damaging them.

I checked the connections between the SDA and SCL pins on my PCB and found a resistance of 1200 ohms. I’m not sure if this is expected or not, but I wanted to bring it to your attention just in case.

If you have any insights about this, I would appreciate it very much.

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The Kicad files:
smart_fsr.kicad_pcb - Google Drive smart_fsr.kicad_sch - Google Drive

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I believe this is outside the scope of the KiCad forums because although your board was designed with KiCad, it is a circuit debugging problem. So this topic is liable to be closed by a mod. But other mods might want chime in first.

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Yeah, I’m giving it a shot here. I’ve tried on other forums, but nobody could help me. If this is a design flaw, I doubt I’ll find the answer anywhere else.

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I didn’t spot an obvious problem with the design with a quick look at it. Was the assembly done correctly? Is the orientation of the ADC correct, are there any solder shorts, etc?

1 Like
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Bad components? Have you tried a logic analyzer to see what code is being sent? I think mine is a $10 version from sleaze bay and sigrok

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Try address 0x28 (shifted up a bit, as r/w is lsb).

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Thanks a lot !! You were right, the ADC was in the wrong orientation. It’s so weird that it would be installed like that. I can’t believe a manufacturer could make such a mistake…
Thanks again for your help :slight_smile:

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Thank you all, you can close this topic if you want :slight_smile:

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