ESP32 beta breakout board

Breakout board for the new ESP32 beta module

Just a little addition to the previous post. I made some photos of the breakout board which was accompanied with the ESP32 beta module. Quite interesting is the thermal pad which is connected to ground. This might be important to solder to the beta module if you clock the chip higher than the standard 80MHz.

Breakout board top pcb
Breakout board bottom pcb


ESP32 beta module HiRes pictures

ESP32 beta test module


I'm glad to be one out of the 200 beta testers for the new Espressif ESP32-chip (it's labeled ESP31B, the obvious name for the beta-ESP32?), which is brand new and adds some functions like Bluetooth (Low Energy) and a second core to the cheap-and-easy ESP8266.

Before soldering the module I took some photos with my Micro Nikkor 105mm/2.8f and stitched them together with Microsoft ICE. This results in photos of about 4400x3100 pixels, which means a quite big download if you click on the preview pictures.

If you want to have a look what I'm currently developing for a new smart home platform using the ESP8266 you can find more info here (CO2 sensor module) and here (Experimental Platform) which is currently in alpha testing.

Concerning the ESP32 Hackaday has a nice news flow and Limor "Ladyada" Fried from Adafruit made a detailed video on the new beta module.

If you are a german reader then you can read my article on the ESP8266 in the current edition of the german Make: magazine (10 pages).

So enjoy the the new module and stay tuned for more news.

Click here for the HiRes pictures: top (~7MB), bottom (~10MB).

ESP32 beta test module top

ESP32 beta test module bottom


ESP8266 breadboard adapter board

I designed a single-sided ESP-12/ ESP-07 breadboard adapter PCB which will be easy to etch and solder for anyone who loves to play with the ESP8266 on a breadboard like me.

Features are:

Image* Fits ESP-12 and ESP-07 module
* Single-sided self-etchable design
* Few, cheap parts in SMD
* Breadboard-style - one row on each side accessible
* Vin >4.5V (max. 7V) input possible with 3V3 onboard voltage regulator (with two capacitors 10µF)
* Power-indicator LED
* (Schottky-) Diode as reverse polarity input protection possible (solder 0 Ohm resistor or just connect the two pads for no protection)
* RST, CH_PD, GPIO0 with 4k7 pull-up resistors on board (resistors can be omitted if remote access of those GPIOs is needed)
* GPIO15 with 4k7 pull-down (see above)
* Tactile switch connected to GPIO0 to get into flash mode
* Single post for 3.3V output near voltage regulator

Parts needed:

  • 1x Voltage Regulator (e.g, AMS1117-3.3V, 800mA)
  • 2x 10µF SMD ceramic capacitors
  • 4x 4.7k SMD Ohm resistors
  • 1x 330 SMD Ohm resistor
  • 1x SMD-LED (1006)
  • 1x 4*4mm SMD tactile switch
  •  2x 1*8 pin header (pitch 2.54mm)
  • optional: 1x Schottky-diode SMD
This is the actual revision 1.0 - improved for:

* Antenna part now protruding the PCB (no traces below antenna)
* Wider traces
* Schottky diode for reverse polarity protection
* 2x 10µF ceramic caps for input/ output of AMS1117
* Single post for 3.3V Output near voltage regulator




ESP8266 - inexpensive IoT

Presentation ESP8266 - Basics and programming examples

On February 2 I had a short presentation at the Makerspace Attraktor in Hamburg on how to use and program the new chinese IoT-IC ESP8266.

The space was quite crowed with more than 40 listeners interested in the new and very inexpensive module with a great range of programming possibilites.

You can find the presentation (pdf in german) here

If you want to stay in touch with new projects or blog entries you can follow me on twitter


Basics about Lithium rechargeable cells

Presentation: Basics, charge and control circuits/ ideas for singe cell lithium rechargeable batteries

Lithium cells are quite powerful
On October 6 I had a short presentation at the Makerspace Attraktor in Hamburg on how to work with rechargeable lithium cells.

A lot of information has to be considered when working with rechargeable lithium cells. Beside the basics, I went into information about the typical charge and discharge characteristics and some circuits and ideas on how to charge and control those cells.

You can find the presentation (pdf in german) here

If you want to stay in touch with new projects or blog entries you can follow me on twitter


XBee remote temperature sensor

There were some questions over time on how the remote sensors on my XBee network are actually wired up and I discovered that I only showed the sensor as is and never explained the wiring. So now this is done with this post and a breadboard picture made with Fritzing:

Remote temperature sensor with XBee

The actual remote sensor has the components just soldered to a stripboard (which works for years now outdoors without any problems). For voltage regulation I use the low quiescent current LDO from Microchip MCP1700-3302E (3.3V, TO-92 style, ~1µA quiescent current consumption). There are 1µF ceramic capacitors both on the raw voltage input and the regulated output (just followed the typical application advice on the datasheet).
The temperature sensor TMP36 is wired to Ground, the Vout is connected to pin 20 of the XBee (AD0/ DIO0/ commissioning button) and Vin is wired to pin 13 (ON/ SLEEP).

The trick with consuming power for the temperature sensor only when the XBee is awake is to wire it to pin 13 (ON/ SLEEP) which is only powered when the XBee is awake.The sensor takes about 50µA when powered and is fast enough to get a temperature measurement while the XBee is not sleeping and takes samples from the AD0-Input (pin 20 XBee).

Temperature sensor on stripboard
My sensors are all powered with three AA cells for now and there is enough room from about 4.8 volts when full and fresh to 3.3 volts when it hits the regulated voltage. The sensor even works below that because I think the supply just gets pulled through the voltage regulator when at or below the regulated voltage.
The circuit draws only about 2.3µA when the XBee sleeps and about 40mA when awake but only for a very short amout of time. So the batteries last about are year or longer.

 There is not much software involved beside configuring the logic on the XBee. Those are my settings:

ATID 2001 (PAN ID)
ATD0 2     pin 0 in analog mode with TMP36
ATIR 3E8  sample rate 1000 millisecs (hex 3E8)
ATSM 4     sleep mode cyclic sleep mode
ATSN B     number of sleep periods (hex B = 12 decimal)

ATSP 7D0  sleep period (hex 7D0 = 2000 ms * 10 = 20 seconds)
ATST 7D0  time before sleep 2 seconds (hex 7D0 = 2000 ms)

Output on a custom made display-box for the kitchen with bus schedule
So the sensor is configured to sleep for four minutes (roughly, the oscillator in the XBee circuit seems to be either imprecise or temperature sensitive) then waking up for two seconds, powering the temperature sensor, sampling two times and then go to sleep again. That's all it does. Voila!

There is still room to improve the project. For example one could add an energy harvesting module to the circuit so that no batteries are used to power the device. Another nice feature would be to take a measurement of the actual battery voltage, which could be done with a simple high resistance voltage divider on one of the analog inputs. It might also be clever not to wire the temperature sensor to pin 20 which is also the comissioning button just in case your XBee is reluctant to wake up.


Malaysia Airlines MH370 whereabouts and the technical part of it

The mystery of the whereabouts of Malaysia Airlines flight MH370 continues and all my thoughts go to the family members having relatives on board of the disappeared Boeing 777-200.

But there is also technical part of the whole story and regardless of the outcome it's worth having a look at the different systems which are involved electronically.
There are four main systems which provide communication between an airplane and the ground. The oldest one, which helped the british army to identify their german counterparts, is the


Primary Radar

High frequent impulses are sent out by a (ground) station into the air and if they are deflected they echo back to the receiver at the (ground) station. The time the signal runs can be calculated and from that the distance and direction of the "object" is derived.
Primary radar signals have to be interpreted so it's sometimes not easy to judge if the "object" is a plane or a flock of birds. There are also limits due to the range of the radar waves and other factors like weather.
Some producer of flying (military) objects - stealth planes - even use their outer shape to avoid any de- or reflection of the radar waves.
To support the findings of the passive primary radar most of the planes, helicopters etc. send out an active transponder signal which is termed


Secondary Radar

Where the word "radar" stands for an active transmission of a signal coming from aboard a flying object. Well known as "transponders" the device sends an active signal which can be of different quality. The earliest systems gave an identifier or answer code (aka "Squawk code") so that the signal of the primary radar and the received signal of the transponder could be matched.
Today a system known as "ADS-B"  - Automatic Dependent Surveillance - Broadcast - is used in many (commercial) airplanes. Once the systems on the plane are on, ADS-B is also automatically activated. Already on ground the system gets automatically interrogated by ground (radar) stations so that the signals can be matched. But those newer systems not only give an identifier, but also lots of other data like speed, altitude, heading and more. The Boeing 777-200 MH370 is equipped with those systems. The range also depends both on the (height/ distance) of the airplane and the quality of the receiving (ground) station.
The frequency of ADS-B is 1090MHz.

Voice Radio Transmissions

Even if many of the processes in aviation are automatically done there is still a lot of live voice communication between pilots an (ground) stations. This is done mostly on VHF (Very high frequency). The normal air radio frequencies are between 108 and 137 MHz. Military often uses other (higher) frequencies.
As with all high frequencies the transfer of messages underlies technical constrains like range, weather, power of the sender, height, and receiver sensitivity. So in some parts of the world there still have to be used less sophisticated radio signals to get contact to the ground.


ACARS - Aircraft Communications Addressing and Reporting System

Another active system is known as ACARS  - Aircraft Communications Addressing and Reporting System. It does what the name implies - it actively, automatically, un-interrogated sends data live to the ground or up to a satellite. Data can be of any quality - from simple status messages to extensive data reports from systems on the plane. Allmost all commercial aircrafts send those data to their headquarters relayed by radio stations around the world.
As allegedly done and reported by the Wall Street Journal the MH370 sent (engine) data for hours into the flight. Depending this is true it is still the question of what quality the data was.
-UPDATE Malaysian officials have told there were no ACARS radio transmission after losing contact to MH370. Last ACARS transmissions were at 01:07AM local time -
The radio transmissions are done in some of the air band frequencies so they underlie the some constraints as mentioned above.

There are other means of identifying flying objects like satellites which are capable of visual or radio tracking, flying radar/ radio stations like AWACS-planes (Airborne Warning And Control System) and other and more secret ways to identfy objects in the airspace.
But those are special ways and normally not involved with commercial aviation.