In my setup the TX pin of the L80 GPS module is connected to a GPIO pin of a processor and that GPIO pin must be temporarily connected to ground (with a switch) in order to upload code to the processor. Up to now all is working fine, but I am wondering if there is some risk to detroy the Tx circuitry in the L80 if Tx is sometimes tied to ground.
I have a question that why the GPIO need to be connected to GND can your code send to the processor? Is it set by your progam?
If the TX pin work in the range of the below table, then all will be fine if you reverse a current limited resistor.
Thank you for your answer.
The processor is an ESP8266 (ESP-01 module ) and the TX pin of the L80 is connected to GPIO0 of the ESP.
In order to upload a new code into the ESP8266 GPIO0 must be set to ground when the ESP is reseted and put in upload mode. So the TX pin is just tied to ground during a short period of time. The problem with the ESP-01 module is that we just have access to 2 GPIOs.
The UART port description for TXD1 in the Data Sheet gives information about the driving capabilities of the port, min and max voltage for HIGH/LOW but I don’t know what happen is the pin is shortly tied to ground from “the outside” of the L80.