[GitHub] [incubator-nuttx] ReimuNotMoe edited a comment on issue #2988: STM32L151 I2C problems

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ReimuNotMoe edited a comment on issue #2988:
URL: https://github.com/apache/incubator-nuttx/issues/2988#issuecomment-798922955


   > Hi @ReimuNotMoe what device are you trying to dump? Do you have a Logic Analyzer to see the bus? Even a "cheaper" logic analyzer can do the trick: https://acassis.wordpress.com/2015/07/19/sigrok-and-a-cheap-saleae-clone-can-save-your-life-i-meant-your-time/
   > This way you can compare the i2ctool command from NuttX against STM32 HAL and the Raspberry Pi i2ctool.
   
   I bought a DSLogic Plus logic analyzer and used it to inspect the i2c lines.
   
   It seems that there are only a bunch of STARTs and STOPs and there are no actual data transfers when running `i2c dump -b 1 -a <addr> 256`, with different devices.
   ![Screenshot_20210314_230049](https://user-images.githubusercontent.com/34613827/111073281-1f419380-8519-11eb-973e-25f870b10041.png)
   
   i2ctool output when dumping an EPSON RTC, all 0xff:
   ![Screenshot_20210314_230317](https://user-images.githubusercontent.com/34613827/111073394-77789580-8519-11eb-94ab-df6af16aeb93.png)
   
   
   i2ctool output when dumping a MCP23017 I/O expander, garbled data:
   ![Screenshot_20210314_230637](https://user-images.githubusercontent.com/34613827/111073503-eeae2980-8519-11eb-868d-b97a75a1f8d7.png)


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