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Si5340 debugging #54
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Suspicion regarding I2V voltage thresholds confirmed. Switching I2C Bus voltage to 3.3V allowed to communicate with Si5340. Contents of the register under address 0x0943 confirm this. Suggestion regarding next release:
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Nice catch! Good that things start to look reasonable ;-) Have you tried reprogramming Si5340 to use 1.8V? I believe under normal circumstances this should not be a problem, as 1.8V is a default option. Using shady source for components is not a reason to complicate the design. However, as shady sources may be our only option these days, we could add a pad for goldpin header for programming Si5340. Then manufacturer can introduce appropriate programming action into the testing procedure (before assembling SOM). |
Yup. I burned this configuration to its NVM. However it has not been yet tested with the bus voltage pulled up to the 1.8 V.
That makes sense, but bear in mind, that pull-up resistors on this bus are placed on the Fast Sevro carrier, not on SoM. What's more the 3.3 V power won't start, if it doesn't detect enable signal, which in this case comes from SoM. |
I tested the I2C connection on hardware with SoM mounted. Works like charm |
It seems that Si5340 is more available now and we can assume it will be set to defaults. However, I suggest we add test points for the purpose of reprogramming in case of someone needs to recover from erronous programming. |
Since, according to its part number, the Si5340 installed on Fast Servo is already pre-programmed, it is suspected that its voltage thresholds are incompatible with the 1.8 V from the SoM. It is currently being investigated:
EDIT: In general, Si5340 NVM is programmable up to three times. Fortunately, it is possible to find out how many times it has been already programmed. One just needs to read a register that contains this information (see: register map section of the reference manual)
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