ESP8266 Community Forum

- Mon Oct 05, 2015 5:56 pm #30609

Hi Bear !
Thanks for your answer.
But i'm using a dedicated 3.3V regulator that is powered directly from the USB-connector and should be able to sink 800mA. The smd-caps are located at the regulators input and output and the 220uF cap is directly soldered to the supply pins of the ESP-module.
And how could a bad supply only affect Bit 3 being set - never ever any other bit !

Sometimes "Ai-Thinker" becomes "Ii-Thinker" so even the very first byte sent is sometimes affected in this way ...

I wanted to use the module with an stm32 application and also develop stand-alone software with Eclipse once in a while.

Any other ideas ?

Hi, the ESPs are unusual in their power demands. They can draw 200mA for short bursts which causes lots of problems that appear in many ways. It's only a guess but I think the ESP is staying above the minimum voltage to function correctly but the USB to TTL is suffering with low voltage dips enough for a zero to appear to be a one. The easy test is to disconnect the 5V feed from the USB to the voltage regulator, and use 5V worth of batteries to feed the regulator.

- Tue Oct 06, 2015 3:46 am #30635 Thanks but still no change

I have now added a 10uF low esr tantal and the 3.3V are now provided by a Li.Ion + 1N4007 Diode in series (to reduce the voltage).
I never before gave one of my IC's such a pure and clean power source

but the result is still something like that:

esp_atr.jpg (2.27 KiB) Viewed 2268 times

- Tue Oct 06, 2015 3:51 am #30636 Well and from my last post one can see that almost every 9th character is 'damaged' by the erroneously Bit 3 set.

Maybe bit banging is used within the 8266 and it is being disturbed by some ISR within itself on a regular basis ?

- Tue Oct 06, 2015 10:04 am #30662 Hi, that should have covered the power issues.
Very strange - every substituted character is exactly (decimal) 8 higher or (binary) 1000 higher than the value you would expect.
As you say its 8th character that is incorrect if you account for CR & LF.
Sorry thats not something I've seen before. The only thing I can think of is to do a loop back test on your USB to TTL to rule that out (connect Tx to Rx, and through a serial monitor send data to see if it is returned correctly).

Code: Select all01100011 = c
01101011 = k

01100100 = d
01101100 = l

00100000 = Space
00101000 = (

01000001 = A
01001001 = I (cap i)

01010100 = T
01011100 = \

01100111 = g
01101111 = o

01110100 = t
01111100 = |