Hi DRice,
Thanks for your reply and apologize for my leave these days
Load on my 4-20mA loop is a 440R, 1/2W resistor(the BLUE one in the second picture-I also debugged it with a 200R resistor before),
Below is the full schematic about AD5421 and AD5700, help check it please(JK2 output DC24V and connect to J7(LOOP+, LOOP-))
For your first pointing "In your second messages,....I also doubted signals from Microcontroller UART then, and I fetched signals pictures on both Microcontroller UART1 and UART2 TXD pins with the same data, they are the same result as belows, so we ignored this issue then.
Thank you very very much!