Unable to Boot and Flash w/ Max31856 connected to WiFi kit8

I am using Heltec ESP8266 OLED 0.96 Wifi kit8 for a temperature measurement project.
this uses adafruit max31856 connected on SPI interface. I have 2 major issues: Boot on Power and Flashing firmware. Looking for some help.

This is the scenario.

  1. The program is inside the esp8266 and running. ( At this stage max31856 is NOT connected). If i power cycle - I HAVE NO ISSUES. Boots fine, and i can see 0 temp values on display (bcos max31856 via spi ) is NOT Connected.

  2. But if I connect Max31856 and then Power Cycle. The program never seems to load. The display is blank ; orange led keeps flashing FOR EVER. Nothing happens. inside program never seems to come up ( bcos i dont see any display). Now, even if i disconnect the power line to max31856 (board has power, just max31856 is disconnected)- nothing happens. After a long time, the orange led stops blinking. Now, if i complely remove power to board and reconnect usb power ( max is still NOT connected), the orange led comes on, but the inside program boots up, and i can see 0 values on oled display. Now if i connect power to max31856, i am able to read the sensor values, they get displayed on oled screen, and all is fine.

My question is: Why is this happening. Obviously when i wire everything and put this project into practical use, i cannot go connect & disconnect max31856 all the time. can you help me.


  1. if max31856 is inside the circuit ( i.e. all connected) - i am getting values displayed on screen. Imagine i plan to make a small change in firmware and flash the board. I CANNOT FLASH from arduino ide. it says, fatal error, timed out waiting for packet header.

  2. BUT, If i disconnect max31856 from circuit, then connect an usb cable from PC to the board, and try to flash it. I HAVE NO PROBLEMS. Flashes perfectly.

So i am not clear why i am having these issues. Any help is much appreciated.