ESP8266 Community Forum

- Sun Feb 07, 2016 2:04 pm #40636 After toying around with esp's on breadboards, I thought it was time to start soldering one on my first PCB. I want to use a ESP-7 to read data from 2 ds18b20 sensors over HTTP.

I thought that by now I know the esp modules well enough to start soldering immediately, before booting it up for the first time. But now that I have everything in place, I seem to have a problem booting it up. I already found out that that the only way to get anything else than garbage out of it is by connecting to it using a unusual baud rate of 74886. When I do that I get:

ets Jan 8 2013,rst cause:2, boot mode:(3,6)

And nothing else, it does not respond to AT commands.

I've hooked the ESP-7 up in the following way:

GPIO15 --> GND
VCC --> 3.3V
GND--> GNG
EN --> 3.3V
TX --> RX on FTDI
RX --> TX on FTDI
GPIO4 --> Data pin of ds18b20
GPIO5 -->Data pin of ds18b20

Schematically it looks like this:



I have the feeling that the problem lies in the power supply to the module. I use a 9v adapter (That I have successfully worked with on ESP-1 and ESP-12 modules) and a LM1117 to convert the power to 3.3 volts. When I connect nothing to the output pin of the LM1117, I get around 3.3v out of it. As soon as I connect the ESP to it, the voltage drops to 1.8v (measurement between gnd and middel output pin), Wich to me doesn't sound good. I do however have no clue as to where I'm going wrong. Any ideas?

Last edited by ErikLem on Tue Feb 09, 2016 3:34 am, edited 1 time in total.

- Sun Feb 07, 2016 2:31 pm #40638 Try to add a big capcitor such 220uF or 470uF nearby the ESP across VCC/GND, it will help to have a stable power.
Also, as a good practice, add some PullUps (around 10K) on both GPIO2/GPIO0 and RES.

- Mon Feb 08, 2016 2:10 pm #40720 Thanks for the advice, will give that a try. One (possibly stupid) question. I can find a lot of capacitors with the right uF, but with a higher voltage (for instance these), but they are for 16v. Is this the maximum voltage to use them with, and can I use them with my 3.3v circuit without problem? Or should I search for different ones?

I did by the way get some more repose from my ESP today (without changing anything). On 115200 baud I now get this:

Code: Select all ets Jan  8 2013,rst cause:2, boot mode:(3,7)

load 0x40100000, len 1396, room 16
tail 4
chksum 0x89
load 0x3ffe8000, len 776, room 4
tail 4
chksum 0xe8
load 0x3ffe8308, len 540, room 4
tail 8
chksum 0xc0
csum 0xc0

2nd boot version : 1.4(b1)
  SPI Speed      : 40MHz
  SPI Mode       : DIO
  SPI Flash Size & Map: 8Mbit(512KB+512KB)
jump to run user1 @ 1000



-----------------------------------------
j¤üFatal exception (0):
apc1=0x40212461, epc2=0x00000000, epc3=0x00000000, excvaddr=0x00000000, depc=0x00000000

 ets Jan  8 2013,rst cause:2, boot mode:(3,6)

ets_main.c


- Mon Feb 08, 2016 2:37 pm #40722 Values I've suggested are just to give you range, it doesn't need to be exact. You can also place 2 capacitors in parallel to achieve total value, example 2x 100uF will give total of 200uF.
Yes, the voltage rating is the maximum the capacitor can tolerate, so 16V is OK, they are only bigger in size compared to same value at max 10V. So, for 3.3V, maybe you should go below 6V, anyway those below are rare.