Upgrading your DPS5005

Johan DPS5005, ESP8266, Hardware, OpenDPS 202 Comments

This is the third article about hacking the DPS5005. Part one covers the reverse engineering of the DPS5005 and part two covers the design of OpenDPS.

 

April 14th 2017 update: is has been verified that OpenDPS can push 5A. Thanks @johannes!

June 9th 2017 update: added a note on saving the STM32 peripheral settings before wiping the internal flash.

August 31st 2017 update: updated article with the new boot loader and a note to test your device prior to unlocking.

 

Although this guide is written for the ‘5005 it should work for the entire DPS family but I only have 5005s to test with. Before we begin I should mention that the stock firmware will be gone permanently. As readout protection is enabled on the STM32, the FW cannot be extracted and I have no source for it. Additionally, I take no responsibility if you destroy your DPS. That said, let the fun begin. You will need a DPS5005 (or similar), an STLink clone and some wire. Either you solder the wire onto the DPS or you can use female-male dupont wires for flashing.

Teardown

First you need to remove the PCB from the (semi) housing. Use a small flat screwdriver to prey the PCB loose from the retaining flaps.

Teardown
Teardown

Be careful not to break the retaining flaps (not that they’re fragile, but still). They are very much needed for holding the front panel in place when you press the buttons.

If you have an older version (below left) you can solder some AWG26 wire onto the SWO and UART ports. It is advisable not to solder pin headers as there is limited room inside the housing. I added dupont jumper housings at the end of the cables to aid in connecting them to the STLink clone and FTDI ditto. Hint: make the cables “stretch” backwards, from the display. For newer versions (below right) the 1.25mm JST-GH there is little room for the SWD wires. As a bonus, you need not solder the UART cables in case you bought one of the “communications versions”.

If you do not want to solder (and do not want any remote control) (and have steady hands) you could connect three female-male dupont cables to the STLink clone and hold them pressed against the DPS while flashing.

Debugger connected, UART cable at the top
Debugger connected, UART cable at the top

Building OpenDPS

With that in place you should install OpenOCD and an ARM GCC toolchain. For GCC, Launchpad is a good place to start. For OpenOCD, YMMW. If you are on macOS you can find OpenOCD here (it installs as /Applications/GNU ARM Eclipse/OpenOCD/0.10.0-201610281609-dev/bin/openocd). With the tools in place you’re ready for the next step.

git clone --recursive https://github.com/kanflo/opendps.git
cd opendps
make -C libopencm3
make -C opendps
make -C dpsboot

Flashing

Next you need to unlock the internal flash of the STM32 before flashing (which causes a complete erase). Start OpenOCD:

cd openocd/scripts
openocd -f interface/stlink-v2.cfg -f target/stm32f1x.cfg

You will receive a few lines of output ending with “Info : stm32f1x.cpu: hardware has 6 breakpoints, 4 watchpoints” if the connection was successful.

Please note! Before you unlock and erase the STM32 flash, you should make a dump of the STM32 peripheral settings of your stock DPS firmware. The DPS hardware might change at any time and if you flash OpenDPS and it does not work because eg. the GPIO pin enabling output power was changed, things get difficult. The ocd-client.py script will assist you now that OpenOCD is running. Please note that OpenOCD might interfere with the stock firmware. When you connect, the stock FW might lock up. First, power on the DPS and make sure the power output is disabled but set to e.g. 5V, start OpenOCD and type:

./ocd-client,py all > 5V-off.txt

If needed, restart the unit (and OpenOCD), enable power output @ 5V and type:

./ocd-client,py all > 5V-on.txt

Rinse and repeat for one or two more voltage levels. Check the log files, there should be no lines saying “Parsing error”. If your OpenDPS does not work, these files will enable me (or someone else, remember this is open source you 😀 ) to pinpoint the problem. Additionally, you should test the device before unlocking it. Enable power, connect something and verify that your unit actually works.

Now let’s wipe that flash. In another terminal:

telnet localhost 4444

and type:

reset halt
flash erase_address unlock 0x08000000 0x10000

You will probably get the following, ending with an error:

Device Security Bit Set
stm32f1x.cpu: target state: halted
target halted due to breakpoint, current mode: Thread
xPSR: 0x61000000 pc: 0x2000003a msp: 0x20000800
stm32x device protected
failed erasing sectors 0 to 63

Keep calm. Restart OpenOCD, toggle power on the DPS and try again. This time you should see:

erased address 0x08000000 (length 65536) in 0.094533s (677.012 KiB/s)

Time to flash (flash the app first, then the boot loader):

make -C opendps flash
make -C dpsboot flash

The last two lines should read:

** Verified OK **
** Resetting Target **

and your DPS5005 is now an OpenDPS 5005.

OpenDPS
OpenDPS, now with wifi

Congratulations! If things went south somwhere, feel free to ask for help in the comments below.

From here you can use the OpenDPS as a stand alone device, control it via a serial port or control it via wifi by connecting an ESP8266.

Short User Manual

When you power on your OpenDPS, the current voltage and current limit settings are displayed and the power output is always disabled. Pressing ON/OFF will enable power output and the display will now show the measured output voltage and the measured current draw. If the screen flashes once and goes back to displaying the voltage/current settings, the over current protection kicked in. Press ON/OFF again to disable the power output.

Press the SET button to go into editing mode. Press the V and A buttons to move between the voltage and current settings. Press the rotary knob to step sideways and turn the knob to change the values. Press SET again to exit editing mode.

Press and hold the knob for two seconds to lock the keys, long press again to unlock. A long press of the SET key will invert the display.

When your OpenDPS starts it will wait for a wifi connection from a connected ESP8266 and the wifi icon will flash at 1Hz. If it does not get a wifi connection, the wifi icon will be turned off after 10 seconds. If there was an error connecting to your wifi network, the wifi icon will flash at 4Hz.

Remote Serial Control

If you soldered wires to the UART port, connect an FTDI adapter and try the dpsctl.py tool:

dpsctl.py -d /dev/tty.usb.yourdevice --ping

The TFT should flash once as a visual indication. If you get ‘Error: timeout talking to device’, check if you swapped RX and TX and/or forgot to connect GND.

The port setting can be set in an environment variable

export DPSIF=/dev/tty.usb.yourdevice

After setting the DPSIF variable, you can try setting the output voltage to 3.3V:

dpsctl.py --voltage 3300

enable the output:

dpsctl.py --power on

check the measurements:

% dpsctl.py --status
V_in : 7.71 V
V_set : 3.30 V
V_out : 3.32 V (on)
I_lim : 0.100 A
I_out : 0.040 A
Run a firmware upgrade over the serial port (extra usable for newer versions where adding SWD is a hassle):
% make -C opendps bin
% dpsctl.py -d /dev/ttyUSB0 -U opendps/opendps.bin
 If serial control is what you aimed for, you can get rid of the annoying flashing wifi icon by adding WIFI=0 when building OpenDPS
make clean ; make WIFI=0 flash

Remote Wifi Control

For wifi control, any good old ESP8266 board with the UART exposed will work. Connect GND, RX and TX, build and flash esp8266-proxy (don’t forget to set your wifi credentials) and you should be good to go.

git clone --recursive https://github.com/superhouse/esp-open-rtos.git
export EOR_ROOT=`pwd`/esp-open-rtos
echo '#define WIFI_SSID "my ssid"' > esp-open-rtos/include/private_ssid_config.h
echo '#define WIFI_PASS "my secret password"' >> esp-open-rtos/include/private_ssid_config.h
cd /path/to/esp8266-proxy
make && make flash

Note that you currently cannot use the master branch on the main ESP Open RTOS repository as my PR for a function needed for multicast has not been merged yet.

When your OpenDPS has connected to your wifi network, try the ‘scan’ command to find out its IP number:

% dpsctl.py --scan
172.16.3.203
1 OpenDPS device found

Next try pinging it:

% dpsctl.py -d 172.16.3.203 --ping

The TFT should flash once as a visual indication. If you get ‘Error: timeout talking to device 172.16.3.203’, check if you swapped RX and TX. The dpsctl.py tool has the same functionality over wifi as well as the serial port.

Sadly, you cannot power your ESP8266 from your OpenDPS. The VDD pin next to the SWO port is connected to U4 (under the TFT), an MD7133H 3.3V regulator which only provides a measly 30mA (yes, thirty). Additionally, this regulator is powered by U3 (on the backside, next to the screw terminal) which is an XL7005A supplying 400mA @ 5V which could be a bit over the edge for a power hungry, cold booting ESP8266.

 

Todos

There are a few todos in the code but overall OpenDPS should be stable for everyday use.

That’s it, have fun hacking your DPS5005!

 

Goodbye ESP3212

Johan ESP32, Hardware Leave a comment

Sometimes you bet on the wrong horse. I put my money down on the ESP3212 as I had seen the images of sample modules and AiThinker seemed to be on the way to mass produce this lovely little thing. As I had a bunch of designs to send off to Dirty PCBs, I quickly whipped up an ESP3212 version of my Esparducam board. The day after the boards went into production (early november IIRC) I read that the ESP3212 was scrapped in favour of the ESP32S. Not a completely bad choice as the 3212 was not pin compatible with Espressifs version of the module. But still.

ESP3212 coaster :)
ESP3212 coaster 🙂

So, if you actually managed to get your hands on a ‘3212 and wish to test it on this board I’d be happy to send one to you for the price of p & p. Goodbye ESP3212, I hardly ever knew you.

The Commadorable 64

Johan ESP8266, Hardware, Retro computing 28 Comments

Update Aug 28th: The BOM for all variants is now on Github. Please see the notes at the end if you want to build a Commadorable 64 yourself.

The ILI9341 based QVGA displays found on eBay for €4 are well suited for making small screenlets telling the current temperature, weather forecasts, traffic situation to work and spreading them over the house. As PCB design is both fun, cheap and rewarding I did a custom PCB for these tiny displays. Actually, I made three, one for each of the 2.2″, 2.4″ and 2.8″ screens. The 2.8″ version has not been produced but the smaller variant have and work well. From 2.4″ and onwards there is (untested) touch support on the screen modules.

The “Hello World” application for this project also named the PCBs. I call them Commadorable 64. Here is why:

LEGO Stormtrooper added for size reference
LEGO Stormtrooper added for size reference

The cursor blinks but I resisted the urge to create an animated GIF. “Commadorable 64” is a play with “Commodore 64” and “adorable”. It has been scientifically proven that those for whom the Commodore 64 played a significant part of their childhood will look at the 2.2″ version of the C64 start screen and react the same way as cat people looking at kittens. Heads will be tilted slightly sideways, smiles appear and sounds like “naaaaaaaw” will be heard. I have one of these at work and depending on childhood experiences people will either go “what?” or “naaaaaaw”.

ESP side
ESP side

The PCB is soldered directly to the pins of the ILI9341 module. Some of these screens will probably end up in other applications in the future. The other day I read about openframe.io and adding support for these would be fun.

The PCBs can be ordered from DirtyPCBs.com, 2.2″ with a bonus AAduino and 2.4″ version with touch. The BOM consists of the usual components for my ESP8266 designs. We have 0603 resistors and capacitors, a 3x6x2.5mm momentary push button [eBay] for displaying the IP address, a SOT23-3 P-mosfet to control the backlight, an LM1117 voltage regulator and a SOD-123FL schottky diode for reverse power protection and optional mini USB connectors. The PCB can be powered in three different ways depending on personal preference (well, four including the esprog interface). There are footprints for normal [eBay] and vertical [eBay] mini USB connectors, depending on if the module is to stand on a table or hang from a wall (Eagle parts available on Github). In addition there is a 0.1″ header for power. All power paths are protected by the diode.

Further update Aug 28th. I see some 20+ orders on DirtyPCBs for both Commadorable 64 variants which is great fun and I would really love to hear what you will build. I have some recommendations you might find useful. I have received a few broken ESP-12e/f modules on eBay over time and one broken ILI9341 module. Because of that I always try the modules before soldering them using my Esparducam board with the ESP Pinlet add on board. When a module passes testing I flash it with the ESP Open RTOS OTA basic demo meaning I can OTA any device directly after soldering. Also, you will note there is no FTDI connector on these boards, the reason is described here. As UART output is still useful, I have one “development” variant with leads from an FTDI connector soldered to the GND/RXI/TXO esprog pads. Oh, and I also have one Commadorable 64 board with a female header for testing the ILI9341 modules before soldering them. If you have any questions about building the boards, sound off in the comments below.

Code and schematics on Github, as always.

Bridging ISM radio and wifi for lunch money

Johan ESP8266, Hardware, IoT, MQTT, RFM69 13 Comments

The ESP8266 has taken the maker community by storm and the hype is well deserved. Before the ESP we had the HopeRF ISM radio RFM12 and its successor RFM69. So is the ESP8266 an RFM69 killer? I would say no. Hell no even 🙂 The RFM69 is still very well suited for certain applications and the ESP8266 will not run for 2+ years on a set of AA batteries. The two can however play nicely together as a low cost ISM/wifi bridge. I did a custom PCB for this in the shape of a somewhat large USB stick, dubbed “Espism”.

 

Currently it works as an ISM sniffer posting the received packets on the MQTT topic espism-<macaddr>. Packets are posted in hex followed by the RSSI value:

espism-5ccf7f147cd Hello from 172.16.3.120
espism-5ccf7f147cd 016340630001000000c375b642[-27]
espism-5ccf7f147cd 630180[-57]

A set of four LEDs indicate received packets. Well three LEDs as I made a mistake on the ground plane. The MQTT server IP and RFM69 network information is hard coded into the binary.

I ported Andreas Heßling’s STM32 RFM driver to the lovely ESP Open RTOS, my swiss army knife for ESP8266 development. The type-A right angle 90 degreee USB connector and 3x6x2.5mm push button can be found for little money on eBay. The push button currently serves no purpose but the plan is to perform a “master reset” of the device using this button. The rest of the BOM consists of 0603 resistors and capacitors, an LM1117 3.3V regulator and a SOT23 P-mosfet for driving the 0603 LEDs. Oh, and the ESP12F talking to an RFM69CW. The BOM should add up to about the price of lunch.

Code and schematics on Github as always.

Factory programming ESP8266 gadgets

Johan ESP8266, Hardware 5 Comments

The FTDI connector can be found on just about any ESP8266 design. If you are building a gadget to be deployed somewhere and not a full blown development board, the FTDI connector is somewhat overkill. And it is quite large. A few pins could be shaved off but we still have a through hole connector invading the other side of the PCB.

I ended up designing my own connector and it has been used sucessfully in all of my recent projects. The connector consists of five test points providing power, GND, TXO, RXI and GPIO0 for boot control. It takes very little single sided PCB space and is inspired by the TagConnect I use at work. Note that the power provided through the connector is unregulated.

I also designed a pogo pin connector to mate the test points and a small board with a DC barrel connector and the FTDI connector. This board has two switches for power and boot mode selection.

If you look carefully on the pogo pin adapter you see that the power pin is somewhat retracted. As the adapter will be hand held, the four other pins can be aligned to the device and with a gentle push power will be applied.

The pins used are P75-B1 1.02 mm (40 mil) [eBay] and the 9x4x8.5mm 3 way switches are also on eBay.

Schematics and my Eagle library with the device connector (“ESPROG-DEVICE”) as always on Github.

The AAduino

Johan Arduino, Hardware, IoT, RFM69 149 Comments

 

More news: read all about the new AAduino Zero.

News: the crowd sourcing campaign for  the AAduino will start soon, sign up at CrowdSupply to be notified! The specs have been beefed with an STM32L0 cpu and the temperature sensor is now an industrial grade TMP102.

Update: you can now order the AAduino PCB from DirtyPCBs.com and get a Commadorable 64 bonus PCB for free.

I have been using Nathan Chantrell’s Tiny328 for quite some time as my swiss army knife ISM radio node. Now I wanted a more slim ISM node as my setup with a Tiny328 on a breadboard is not very “deployable”. I could of course 3D print a case for the Tiny328 but I have limited access to 3D printers and do not feel I have the time to explore that exciting part of the maker world just yet. This leaves me with finding off the shelf project boxes with a compartment for 2x AA batteries and the “radioduino” (and in an acceptable form factor). That search came up disappointingly, and surprisingly, short. I did have a set of standard eBay AA battery holders and looking at the 3x variant it occured to me. I needed to shrink the radio node, and the AAduino was born.

Honey, I shrunk the radioduino!

The AAduino is an wireless Arduino clone the size of an AA battery with Keystone battery terminals rotated 180° to act as positive and negative terminals. It is powered by an ATMega328p and is fitted with an RFM69C companion. There is room for two DS18B20 temperature sensors and an indicator LED.

I still think it looks a bit weird :)
I still think it looks a bit weird 🙂

It runs at 8Mhz to allow for greater life span since the CPU can run at a lower voltage. I have fused the 328 to brown out at 1.7V which is a bit out of spec at 8Mhz and slightly below what the RFM69C needs. Running at 4Mhz would be more suitable but I will see how well the node performs when the batteries are draining out.

AAduino, RFM69C side
AAduino, RFM69C side

Since the RFM69C is somewhat wider than an AA battery I used a file to make it slightly narrower. There is some room for that kind of modification without damaging the module. Update, the RFM69C will fit without modification. Next I clipped the legs of the DS18B20 until about 5mm remained and soldered it to the 3x pin header on the AAduino. I then drilled a hole in the battery box where the sensor can protrude and a small hole for the LED to shine through. The wire out of the battery box was cut, shorted and stuffed away inside the box.

AAduino inside 3xAA box
AAduino inside 3xAA box

I use battery terminals from Keystone available from RS Components, positive and negative. There seems to be a cheap eBay alternative but I have not tested those. The + and – markings on the PCB indicates (this is important, read carefully) the positive and negative poles of the battery we are pretending the AAduino is. The Keystone spring contact should be soldered to the + marking and the button contact to the – marking. There is no protection diode here so be careful. Also note! If you want to power the AAduino from a bench power supply, connect the power supply’s black negative lead to the + marking and the red positive lead to the – marking.

aaduino-v2

The 3xAA boxes are also from eBay and there seem to be two different types. One that is really good and one that is really crappy. I will let you in on the secret of buying the correct one. The good ones have a nice build quality and plastics and look like this. Note the rectangular piece of plastic below the battery compartment extending from side to side.

Good 3xAA holder
Good 3xAA holder

Looking at the crappy ones, well you can tell can’t you? In the top left corner it seems someone used a soldering iron on the poor thing. The lid does not snap in place very well and the plastics is really cheap.

Crappy 3xAA holder
Crappy 3xAA holder

Code, schematics and BOM on Github, as always.

Building the Esparducam

Johan ESP8266, Hardware, IoT 18 Comments

I have had some questions about the possibility to purchase Esparducam boards and also about the bill of material. While I am looking into selling spare boards, here are some instructions about building the boards. Here is the link to order the PCBs [dirtypcbs.com].

Bare PCBs

If you have never tried building surface mounted boards yourself I highly recommend you try it! I started here [nathan.chantrell.net] and googled my way from there.

Here is the BOM with some eBay links:

C1 1uF capacitor 0603
C2 0.1uF capacitor  0603
C3 1uF capacitor  0603
C4 10uF capacitor  0603
C6 0.1uF capacitor  0603
J1 6 pin 2.54mm male header (angle) [eBay]
JP1 8 pin 2.54mm female header (for the Arducam Mini) [eBay]
JP9 Power jack 5.5×2.1mm [eBay]
R1 4k7 0603
R2 4k7 0603
R3 4k7 0603
R4 4k7 0603
S1,S2 Momentary switch [eBay]
U1 NCP1117 (or LM1117) 3.3V regulator [eBay]
X1 ESP-12f

The following parts are optional depending on what you want to do with your board:

Reverse current protection

D1 SOD-123FL, schottky diode for reverse current protection [eBay],
If you feel brave you can bypass the diode by placing a blob of solder across SJ2 on the back of the board.

Adding motion detection

If you want to attach a PIR [eBay] you need:
J2 JST ZH connector, 3 pin [eBay]
R6 220k 0603
R7 100k 0603
R6 and R7 was going to be a voltage divider that I messed up leaving R7 optional. Please note that the PIR does not work at 3.3V. To bypass this without adding a 5V regulator I simply feed the PIR with the raw board voltage which in my case is 5V.

Controlling power to the Arducam Mini

If you want to be able to control the power to the Arducam Mini board you need Q2 and R5. If you feel ok to have power constantly enabled simple place a blob of solder across SJ1 at the back of the board.
Q2 P mosfet, SOT-23 [eBay]
R5 4k7 0605

External flash

The external SPI flash is also optional. Please note that the footprint is somewhat too narrow, some flashes might not fit.
U2 SPI flash SOIC-8
C5 0.1uF 0603

Adding header pins

These optional headers are for attaching add-on boards or pins for taking measurements
JP3, JP6 8 pin 2.54mm male header
JP4,JP5 8 pin 2.54mm female header

That’s it, good luck!

Building a low cost wifi camera

Johan Cameras, ESP8266, IoT 76 Comments

Update! Here is a post with the BOM for the project.

Sometime ago I came across the Arducam Mini which is quite a nice camera module from UCTronics. It is a small PCB with a two megapixel OmniVision OV2640 sensor, an interchangeable lens and an FPGA to do the heavy lifting of image processing and JPEG encoding. Priced at around 24 Euros (lens included) you can easily buy a few without hurting your wallet and combined with an ESP8266 you can build quite a low cost wifi camera. Or several. Because designing and building PCBs is both fun and inexpensive I designed a board to go with the ESP8266/Arducam Mini combo, aptly named the Esparducam. And uniquely named too, try googeling for “esparducam“. Heck, even the domain name is available at the time of writing 🙂

The Espaducam board
The Espaducam board

Anyhow. The Esparducam board is a development board for the Arducam Mini module and is quite well suited for ESP8266 development in general.

Espaducam with Arducam Mini module
Espaducam with Arducam Mini module

The board is powered through a barrel connector at a minimum of 5V (upper limit untested) and all the IO pins on the ESP8266 are available on pin headers. The double rows are intended for the design of small breakout boards that sit on the inner 0.1″ aligned headers while the outer headers allow for connecting logic analyzers/oscilloscopes and so on. The Arducam Mini module plugs right into the front header and the standard FTDI connector is at the back of the board.

Image quality is, imho, quite decent at this price point, here are a few samples.

An optional SPI flash can be mounted for image storage and you can connect a standard eBay PIR module to the white JST header next to the FTDI connector if you want to build a motion triggered camera.

I am no hardware engineer but if you are and you find any silly design mistakes please let me know.

Schematics
Schematics

You can order the Esparducam board form DirtyPBCs and I would love to know if you build one. I plan to build a few for house monitoring, kite photography, reading my water meter and whatever else I can come up with.

The demo application listens to port 80 for HTTP GETs and will capture and return an image. It also has a command line interface on the serial port and the command ‘upload:<ip number>’ will capture an image and upload it via HTTP. A Python script is included that will receive and display the image using your system’s default image viewer. Note that the demo application is just that, a demo application. It does not handle simultaneous clients, errors or anything else that occurs in the real world.

IMG_3761Lastly a note about the lens. It uses a mount called M12xP0.5 and there are plenty of lenses to choose between. The one included with the Arducam Mini module has about the same field of view as a normal 50mm lens on a full frame DSLR. I would recommend getting a 3.2mm lens or shorter for some more wide angle if you plan to use the module for surveillance applications. The 3.2mm lens (called LS-40136) can focus at a very short distance making it a candidate for water meter reading applications.

I have yet to try the even shorter ones like the LS-20150 at 2.8mm or the LS-40166 at 2.6mm.

The Esparducam turned out so nice it became my preferred ESP8266 development board, why is a different post.

Code and hardware schematics as always on Github.

 

 

A versatile ESP8266 development board

Johan ESP8266, IoT, RFM69 17 Comments

This is followup to my post about building a low cost wifi camera. I mentioned that the Esparducam board is well suited for ESP8266 development in general and here is why. In addition to the Esparducam board I also designed a number of addon boards. The boards are very small (21×26 mm) meaning you can fit two of them into a standard 50×50 mm PCB you can get produced for very little money. If you want to try a new component or connector and perhaps a newly designed footprint, make a “boardlet” and try it on the Esparducam.

The RFM69C breakout
The RFM69C breakout board

The “ISM boardlet” mounts an RFM96C for building a low cost ISM to Wifi gateway. The board has an optional LED (driven by a mosfet) for link indication. I ported André Heßling’s RFM69-STM32 driver for this board and even though I have not had the time to test that much, basic transmission works.

The ESP Pinlet
The ESP Pinlet

The next board, the esp-pinlet, serves as a test bench for ESP12 family modules. After soldering an ESP12e module to an Esparducam board I noticed it would not connect to my Wifi network. For the price of ESP8266 modules, I cannot complain about broken modules but I want to make sure the modules I mount on my boards actually work before soldering. So how do we test ESP12 modules without soldering? Pogo pins! The pinlet board has 1.02mm (40 mil) holes for pogo pins that allows for an ESP12 module to be firmly pressed against the pins while flashed and tested. You can find these on eBay.

Look ma, no solder!
Look ma, no solder!

Schematics on Github.

Update on April 27th

Th pogo pins I used initially where not that good as the needle like shape made them get stuck in some of the ESP12 modules. A much better alternative is the P75-E2 [eBay] type of pin (still 1.02mm / 40mil):

P75-E2 pins
P75-E2 pins

If you plan on building a pinlet board, make use of the fact that you get ~10 in each order to help with alignment.

Pin alignment
Pin alignment

The stack here (top to bottom) is the board having the pins mounted, a spacer board (the red one), five pinlet boards for alignment and at the bottom one board flipped upside down to keep the pins from sliding downwards. The package is fixed with tape and ready for solder.