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By louis
#66032 Hi fellow ESP users. I am having a problem with my NodeMCU. If I connect the TXD0 pin to low via resistor the device will not boot and run my app. Seems to go into flash mode. However if I tie it to 3V3 via resistor all is fine.

The reason I am doing this is to convert the 3v3 UART lines to RS232 levels without using a MAX chip. Not ideal for TX, but works fine. Using the circuit below (top part):


The cap in series with resistor from TTL (NodeMCU) TXD to VCC works. But then I have to always power cycle to reset so that cap can discharge.

My real question is why does the device not boot into program when TXD0 is LOW.