I have a project with an arduino hooked up to a ESP8266 to transmit data over wifi. My problem is that I forgot to upload my adjusted final program to my nano before I soldered it to the PCB board. This pcb board involves a direct connection between the serial pins of the arduino and the esp8266. For some reason when these are connected, even when there is no power going to the eSP8266 it prevents the computer from uploading the program to the arduino. Does any one know why this is happening? ANd is there something I can do short of cutting the traces between the Serial connections?
Below is the error message from the uploader. Again if the serial pins are disconnected, it uploads fine, so I am sure that is the source of the problem. I tried pulling the rx and tx pins both high and low on the ESP8266 with no success.
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0xbc
Hi,
I haven't looked at the Arduino-nano schematic, but in most Arduino applications, you will definitely need to find a way to disconnect at least the "RX" pin (D0). If the ESP8266 is powered at the same time, you can likely leave the "TX" pin (D1) connected. If your PCB has a hard connection, then a trace-cut may be your only option. I always put in a simple 2-pin jumper just for this purpose (to disconnect RX).
Your best bet is as uptoolate says.
Either cut the traces or remove the esp from the assembly.
I would do both TX and RX myself as they are often both used for comms on uploads.
If you have to rework the board a little then why not do both at the same time as it may help you out down the road a little.
I guess what I don't understand is why it doesn't work when I have the other board powered down. I don't quite see how electronically it is any different than just having free wires hanging off. i suppose I still have the ground connected between the two board and maybe it's pulling the pins low... I guess I'll be cutting some traces then.
jeffpkamp:
I guess what I don't understand is why it doesn't work when I have the other board powered down.
Parasitic powering. The 5V (3.3V) on the TX pin of the main micro powers the ESP via the protection diodes in the ESP; look at the internal schematics of the ESP. Below a bit of ASCII art (only the relevant diode drawn)
Vcc o-----+----------
|
_|_
/ \ D
---
|
ESP RX o-----+----------
As you can see, 5V (3.3.V) on the ESP RX pin flows through diode D to Vcc and powers the rest of the ESP.