ESP8266 Community Forum

- Sat Feb 27, 2016 7:50 pm #42025 Hi all .
My last project consider an heartbeat on my ESP-12E. I have done this heartbeat using the schema attached, a simple missing pulse made with a 555. The ESP sends a pulse every 100ms, if it stops this pulse, the heartbeat sends a pulse to a bistable electrovalve to close it. The heartbeat is powered by a 9v Battery (like electrovalve voltage) and the pin used to send the pulse is the TX pin of my ESP. I'm using it , because the others are used by the electrovalves.
The problem is that i need to connect the heartbeat only after the boot of the ESP (1 second after the switch on is enough), if i connect it and then switch on the ESP, the ESP doesn't run.
Can you explain me why? Maybe the TX must be in a specific state during the boot?
thanks

- Sat Feb 27, 2016 7:53 pm #42026

Hi all .
My last project consider an heartbeat on my ESP-12E. I have done this heartbeat using the schema attached, a simple missing pulse made with a 555. The ESP sends a pulse every 100ms, if it stops this pulse, the heartbeat sends a pulse to a bistable electrovalve to close it. The heartbeat is powered by a 9v Battery (like electrovalve voltage) and the pin used to send the pulse is the TX pin of my ESP. I'm using it , because the others are used by the electrovalves.
The problem is that i need to connect the heartbeat only after the boot of the ESP (1 second after the switch on is enough), if i connect it and then switch on the ESP, the ESP doesn't run.
Can you explain me why? Maybe the TX must be in a specific state during the boot?
thanks

Attachments

sorry .. the schema
heartbeat.png (11.57 KiB) Viewed 2740 times

- Sun Feb 28, 2016 8:38 am #42042 Someone mentioned recently about a new discovery that TX pin need to be PullUp at boot time like GPIO2/GPIO0.
So, you probably need to use a MOSFET instead of NPN and adding a PullUp resistor.

- Wed Mar 02, 2016 2:09 pm #42255 Hi, i think so!
But if i will use the Rx pin. For me i suppose it is the same

Thanks