Connecting esp32 TX to AT8951 RX (UART)

Other Hardware General Electronics
1

Hi,

I am trying to control some old AT8951 controlled sevseg displays over wifi, I am using NodeECU ESP32S for that. The AT8951 uart RX pin is pulled high by default, which I have learned the hard way, because it fried my esp32 board (which is 3.3v, the AT8951 is 5V TTL). It is only one way communication esp32 TX > AT8951 RX, ist there any easy solution with a diode for example or do I have to use level converter of some sort?

Thanks,
Lu.

2

A bi-directional level shifter board is ideal because it shifts the voltage in both directions so you get 3.3V signals on the 3.3V side and 5V approximately signals on the 5V side. At a push you could maybe use a resistor divider with a suitable ratio, e.g. 3.3k/6.8k across the 5V side. This will provide a signal of approximately 3.3v amplitude across the 6.8k resistor, but the input to the 5.5V side will still be at only 3.3V.