[closed,bug found]Fail to write wiper register from specific value through IIC for MCP4018-503

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I used MCP4018-503 composed with MIC3711YMT to get variant voltage on fly.

I'm puzzled by a interesting problem:

The write process will fail if value reached a specific one.

The wiper range for 4018 is from 127 down to 0, you can set wiper register with valus between 0~127 through IIC.

For my case, from 120 down to 26 is OK,

fail from 23, and it will keep failing from that on even you try to do the software reset operation.

The only way to stop is hardware reset, sometimes need to power off.

 

It is really strange,

It should keep failing for all values if circuit is wrong.

The resister array is isolated to IIC from hardware view,  different resist should not infect the IIC function.

 

It should keep failing for all values if code is not right too.

 

 

 

 

This topic has a solution.
Last Edited: Sat. May 2, 2020 - 03:18 PM
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You're making an assumption. Have you determined if it is the hardware or the software?

 

Interesting that Microchip declare the mic37112 as obsolete and don't publish a datasheet for it.

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Found the bug,hardware issue.

 

VSS not connected to GND!