U0TXD=GPIO1

[SpenZerX]

Hi Espressif,

what hardware (max current draw?, only LED? Transistor possible?) can be connected to U0TXD=GPIO1
to boot successful and save reach UserInit after a cold boot? Or should this be evaluated by testing?

In UserInit U0TXD-Pin will be connected as GPIO1-output. (->max output 10mA after this configuration?)


I know there is debug output of ROM-boot loader, and this is misuse. But GPIOs are limited and normally a LED is connected. I dont need serial in normal state.

Thanks

[Espressif_Kelly]

Dear SpenZerX,

1.what hardware (max current draw?, only LED? Transistor possible?) can be connected to U0TXD=GPIO1 to boot successful and save reach UserInit after a cold boot? Or should this be evaluated by testing?

->U0TXD+U0RXD or GPIO2+U0RXD usually can be used to download firmware into external spi flash.
Besides, U0TXD is also a strapping pin for chip_test_mode(1: normal mode; 0: chip_test_mode). Thus, U0TXD can't be pulled down just when the system is powered on.


2. In UserInit U0TXD-Pin will be connected as GPIO1-output. (->max output 10mA after this configuration?)
->When U0TXD is reused as GPIO1, the source current of this GPIO is 12mA and sink current can be greater than 12mA.


3. I know there is debug output of ROM-boot loader, and this is misuse. But GPIOs are limited and normally a LED is connected. I dont need serial in normal state.
->It is ok for you to connect a led in this pin to vdd.

Thanks.

[nirajmahapatro]

Hello Kelly,

"Besides, U0TXD is also a strapping pin for chip_test_mode(1: normal mode; 0: chip_test_mode). Thus, U0TXD can't be pulled down just when the system is powered on. "

Can this behavior be changed? Is there a way, probably tweaking the bootloader, where the strapping for chip_test_mode is disabled.
I have an diode connected to gnd from UOTXD which is avoiding to boot the ESP8266 in normal mode.

Thanks
Niraj