SC18IM704 does not work

[2282242919]

Hi everyone!

I used STM32F407 for UART communication with SC18IM704 chip. The UART peripheral of STM32 successfully sent data to tx, but there was no feedback from SC18IM704 on rx.when board is power on.UART baud rate is 9600 bit/s.

The schematic diagram of the board is shown in the figure.

I use the Read version function ID command of SC18IM704 .shown in the figure

No data feedback provided of SC18IM704

[JozefKozon]

Hi, 

according to the SC18IM704 datasheet, after power up the SC18IM704 send two bytes to the host. Do you receive these two bytes after power up? 

If you are not receiving these two bytes, please check if the RESET pin is high. Please remove the 10k pull-up resistors on the TX and RX lines. Only the RX pin requires pull-up resistor and only if you want to keep the SC18IM704 in Deep Power-down mode. Otherwise no pull-up resistors should be on the TX and RX lines.

With Best Regards,

Jozef

[2282242919]

hello Jozef:

I check the RESET pin of SC18IM704 is high(3.3V) by oscilloscope.after power up the SC18IM704. I not find the two bytes('OK') by oscilloscope. I removed the 10k pull-up resistors on the TX and RX lines. I use four SC18IM704 chips ,and the situation is the same. I don't know how to solve this problem，please help me.

[JozefKozon]

Hello, 

thank you for confirmation. Please remove the R106 resistor, to disconnect the TX pin from your MCU. To make sure, that the TX pin is floating (not held high by your MCU). Then power up the SC18IM704 and measure the TX pin on the SC18IM704 with an oscilloscope to look for the "OK", the two bytes 0x4F and 0x4B. 

If you still don't see the "OK" please conduct the reset with the RESET pin. 

1. Watch TX with oscilloscope

2. Hold RESET LOW (GND) for ~10 ms

3. Release to HIGH

4. See if the "OK" appears

With Best Regards,

Jozef