No MAC address on power up

[haagden]

I have a custom designed board with an esp8266-12f. I want to upload new firmware but cannot seem to be able to enter boot mode. On power up I get the expected response of 'ready' (viewed on a serial terminal) using 115200 baud but no response to inputs (AT commands) from the terminal which is set to provide CR/LF following the command input.

Have I got a bad device, when and how does the MAC address get 'burnt' to the device? I have a digital scope, all the pre-requisites (GPIO15 grounded, GPIO02 pulled high through resistor, GPIO0 grounded for boot mode) look to be correct. I have 100uf tantalums both before and after the 3.3V (TPS77733) regulator but the Nodemcu flash tool never shows the MAC address which it should if the system powers up in boot mode.

I am powering the PCB from the 5V supply from a Raspberrypi USB port (should provide 500 mA) and using an FTDI converter to provide the level changing for the serial interface (Rxd & Txd). I do NOT use the Vcc from the FTDI interface.

I did initially use 5V signals on the serial interface, would this have damaged the ESP8266. I just never seem to get anything in response to inputs to the ESP8266 from a terminal program.

[haagden]

Problem solved. As is almost always the case, the problem was with the power source to the ESP8266. The design incorporated a battery charge controller MCP73871 powered by an 5V USB port. Whilst this could potentially source 600mA the charge controller limited the current. Connecting the battery allowed current demand in excess of that sourced by the co,nyroller to be provided by the battery. This, together with a 100 uF capacitor at both the input and output of the TPS77733 LDO seems to have rectified the problem.