Ltc2439-1 in SPI communication data output is high first out or low first out?

Looking at the timing diagram of Figure 3a, I think there could be something wrong with your communication with the ADC. The first two bits should always be zeros. Can you provide an oscilloscope photo showing CSL, SCK, SDI and SDO? A schematic of your circuit would also be helpful.

• Read channel 0 data, single-end input, single chip sends 0XB0, right

I do not understand what you are asking me. 

wonder if it is possible for the MCU to detect the BUSY signal according to the circuit shown in the picture?

LTC2488 does not have a BUSY pin. TLP291-1 is not recommended for new designs. SDO can be used indirectly to generate BUSY but the data sheet does not indicate that SDO can drive the TLP291-1 diode.

• It's LTC2448

At present, the chip is replaced by LTC2448, and the data is 24 bits. How to convert the voltage value?

Waiting for your reply, thank you!

I'm not sure what you mean by how to convert the voltage value.

For example, the 24-bit read value is 00123456 hexadecimal, how to convert to the actual value of the voltage?

If you look at Table 1 of the data sheet you will see that if the first 4 bits of the output word are 0s, that indicates that the input voltage is below -Full Scale (-0.5*Vref). Let me pick a value that is not railed for an example. 20111111 hexadecimal. According to Table 1, if the first 4 bits are a Hex 2 (0010) then Vin is between 0V and 0.5*Vref. Bits 28 to 5 are the 24-bit conversion result MSB first. Bits 4 to 0 are sub LSBs that can be included if desired or ignored. For simplicity I will ignore the sub LSBs. This results in a 24-bit output code of 008888 hex. Converting that to decimal produces 34952. Dividing that by 2^24 yields 0.0020833015. Multiplying that by the reference voltage (5V) will produce the input voltage, in this case 0.0104165077V.

Thank you for your reply!Another question is, how to convert the GPIO voltage read by ltc6811-2 chip to the actual voltage value?

VREF2 Is the 34-pin output voltage of ltc6811-2。T1~T5 is connected to the MCU, JT1 is the connector, connected to the temperature probe, measuring temperature range is -55~100℃，Refer to the development board circuit。

• Waiting for your reply, thank you！

That question should be asked in the Energy Monitoring and Metering Forum.

That question should be asked in the Energy Monitoring and Metering Forum.