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sim7000 level shifter txb0104v vs txb0108

narendra verma
Prodigy 10 points
Part Number: TXB0104
Other Parts Discussed in Thread: TXB0108, SN74AXC4T245, SN74AXC8T245

 found, below in datasheet of sm7000 

but I made schematic using txb0104 ?

could pls help me identifying what change in txb0108 ...    i see change in 

A8 & B8 with 50k resistor in not my schematic 

Pls i need help in sim7000 connection with ESP8266, I made circuit schematic as fellows:  https://drive.google.com/file/d/1DmEGsg21y8fWkgbwrTyIfXZmvKAUnUXp/view?usp=sharingI'm able to control sim7000 with its USB function But not able to use its Uart (TX RX Pins. for AT commands)I used level shifter TXb0104 for talking with my ESP8266 controller, but no luck ... No AT response.

Using High logic 3.3V or 5V with transistor to safely turn on Sim7000, I'm getting 0.8V or sometimes below volt on power pin while 1.6-1.8V on reset pin.

But no AT command response through TX RX (UART.) Tried both 115200, 9600 baud rate but still no luck in AT response 

here my AT command ...

https://drive.google.com/file/d/1NqhqkOlmVqB1gQw_t5X2NXKlVegjoEcr/view?usp=sharing

: 

  • 0
    TI__Mastermind 46045 points

    Hi Narendra,

    For UART I would actually recommend using the SN74AXC8T245 (8 channel) or the SN74AXC4T245 (4 channel). TXB level shifters are more suitable for bi-directional data lines and as we see in the schematic, we know the direction of these unidirectional signals. It's not drop in compatible, but it will likely fix the issue you are facing with the TXB device.