Manufacturer's page of the LTC6811: https://www.analog.com/en/products/ltc6811-1.html.
According to that page, there are two demo boards. Both come with a schematic. Which one do you have ?
What is a PEC ?
Do you use a sketch ?
What voltages are allowed for the SPI bus ? I can not find that in the datasheet, so I don't know if it is allowed to connect it with an Arduino Uno. It seems to be 3.3V signals.
More links please !
Check what you have written on this forum. You can fix a typo.
What is a DB1894B ?
According to the LTC6811 datasheet, page 7, the VREGD "Digital Supply Voltage" is 2.7 to 3.6V. On the same page it says that VIH(SPI) is minimal 2.3V, however the maximum voltage of the SPI signals is not specified.
Page 30 tells that the VREG should be between 4.5V and 5.5V and the Digital Power Supply VREGD is 2.7V to 3.6V, the value is determined by internal components.
I think that means that the digital interface for the SPI bus runs internally at 3.3V.
On the other hand, at page 15 is written: "GPIO[1:5]: General Purpose I/O. Can be used as digital inputs or digital outputs, or as analog inputs with a measurement range from V – to 5V. GPIO[3:5] can be used as an I2C or SPI port".
Perhaps the digital inputs accept 5V signals and perhaps the SDO is open source on purpose to make it compatible with a 5V SPI interface.
Since the maximum voltage for VIH(SPI) is not specified, then it should work with 5V.
Now I would like to understand how can i control if board using LTC6811 or LTC6813.
I have to understand how can i use different command or settings to check wich LTC is used.
Can you tell me what procedure you followed to get the communication going. I am also facing the same issue.
I am always getting PEC error. I have made the connections as written in your first post.