Using IDE 1. 6.8 and Adafruit Huzzah board ( same thing with ESP generic)
Using an RFduino USB/Uart that is 3.3V rated, TX/RX and Reset only ( not using reset)
Using a separate 3.3V supply to ESP
Out with the trusty scope to have a look and everytime I have a synch fail the waveform on ESP RX is less then 1V p-p. so perhaps the handshake is failing due to lack of voltage signal and hence sycnh problems.
If I do get a successful download then a good waveform 3Vp-p
Also I have noticed that if I send single characters via Term at 115600 baud as a test then I often see that the character does not 'reach' the Rx pin on the ESP when the ESP is in upload mode yet there is no problem that I can see when the ESP is powered down. Again a good 3.3Vp-p
Is there a possibility of an impedance mismatch, or a strange hardware mismatch in the ESP? Has anyone else scoped the TX/RX?
My scope is not so flash that I can capture and download to this site. I would be interested in comments and waveforms.