When I’m on my PC, I use DNS Jumper to switch between Google and Getflix DNS servers. However, when I wanted to watch US Netflix on my LG TV I had to manually change the network configuration, not very comfortable with a remote. I couldn’t either leave the Getflix DNS always configured, as my family wouldn’t want to have English-only flicks nor lose some Italian-only movies Netflix probably offers.

The solution was to use my Raspberry Pi as a DNS server, point the TV to it and integrate a script into Home Assistant so I could manage the whole thing from my phone together with other lights and switches in my house.

The first thing to do is to install dnsmasq, a DNS and DHCP server, on your Pi:

sudo apt-get install dnsmasq

I wasn’t interested on the DHCP part so I haven’t enabled it. By looking at the dnsmasq manual I found some interesting and useful features:

• dnsmasq gets its upstream (i.e. ‘reference’) DNS servers from /etc/resolv.conf, a file that on my Pi was auto-generated by resolvconf. You can either change resolvconf configuration (via the /etc/resolveconf.conf file) or force dnsmasq to ignore the file and use specific DNS servers. I chose the second option.
• dnsmasq caches DNS queries, which is a good thing in general but bad for our use case. By sending a SIGHUP to its process, we can force a cache cleaning.

We will now create two copies of the dnsmasq config file and a very simple script that switches between them.

We need to add (or uncomment) the following lines in the /etc/dnsmasq.conf file:

# ignore the /etc/resolv.conf file
no-resolv

# probably redundant: ignore changes in /etc/resolv.conf
no-poll

listen-address=127.0.0.1
listen-address=YOUR_LAN_IP_ADDRESS

We can now copy the files:

sudo cp /etc/dnsmasq.conf /etc/dnsmasq.nflx.conf
sudo cp /etc/dnsmasq.conf /etc/dnsmasq.goog.conf

Now we force Getflix DNS servers, appending the following to the /etc/dnsmasq.nflx.conf config file:

server=GETFLIX_DNS_SERVER_1
server=GETFLIX_DNS_SERVER_2

We then do the same for the /etc/dnsmasq.goog.conf file:

server=8.8.8.8
server=8.8.4.4

We can now write the script that handles the change between the two files. We  touch /home/pi/dnschange and edit it with our favorite text editor.

if [ "$1" = "google" ]; then
        cp /etc/dnsmasq.goog.conf /etc/dnsmasq.conf
        echo "Google DNS servers restored."
fi

if [ "$1" = "netflix" ]; then
        cp /etc/dnsmasq.nflx.conf /etc/dnsmasq.conf
        echo "Getflix DNS set."
fi

systemctl restart dnsmasq.service
killall -s SIGHUP dnsmasq
echo "dnsmasq restarted."

Make the script executable:

chmod +x /home/pi/dnschange

We’re about done. By running sudo /home/pi/dnschange netflix we will be able to watch the US Netflix, and by running sudo /home/pi/dnschange google  we will revert back to Google DNS servers.

You can make sure the script is working by running cat /etc/dnsmasq.conf | grep server= and see if the file has the right servers inside.

Still, it would be quite unpractical to SSH into our Pi from the couch and run the two commands. Let’s integrate the thing with Home Assistant so we can easily run the script from our mobile web browser.

Edit the HA config file and add the following lines. For me, it’s in /home/homeassistant/.homeassistant/configuration.yaml:

switch:
  platform: command_line
  switches:
    nflx_unblocker:
      friendly_name: "Netflix US"
      command_on: "sudo /home/pi/dnschange netflix"
      command_off: "sudo /home/pi/dnschange google"

Then, let’s add the homeassistant user to sudoers so it can run the commands as root without asking for a password (make sure your network is secure!), by editing the sudoers file

sudo visudo

and adding the following line:

homeassistant ALL=NOPASSWD: ALL

We can now restart Home Assistant and we should be ready to go.

sudo systemctl restart home-assistant@homeassistant.service

This is how the switch looks on my phone. I’m still a Home Assistant newbie so the interface is a bit bare, but I plan on adding automatic blinds and more lights in the coming weeks.

It’s quite a dirty hack and could be integrated better (e.g. we could make HA verify the DNS change) but it works perfectly for me: the only thing I have to do is kill and re-open the Netflix app on my TV. Happy watching!

I released a newer version of my ATX Breakout Board. After receiving a lot of requests, I also printed some PCBs (10x blue, 10x red) and will print more after thorough testing of the current revision.

Features and additions added from the older version:

• Thickened many traces, removed pin headers in the middle of the board and added one behind each binding post (up to 5 output pins per voltage line, with no risk of burning any traces).
• Added resistors to the USB ports (on the back of the board). You may want to use them for USB identification, as they are cheaper and easier to find than the TPS2513. Adafruit link for more info: https://learn.adafruit.com/minty-boost/icharging
• Moved LM317 so that you can mount it horizontally + used a footprint with longpads, should you want to solder wires to an external voltage reg + heatsink.
• Prototyping area added at the top left of the board. Not sure if it will ever come useful, but I had some empty space there. You have easy access to the 3V3 and 5V lines.
• Moved/rearranged several parts (pot, switch, LEDs) in order to draw shorter and cleaner traces.

New parts list:

• C1, C3: 0.1uF 0805 SMD capacitors.
• C2: 1uF 0805 SMD capacitor.
• F1, F2, F3, F4: 1812 SMD PTC resettable fuses. (Littelfuse ones should work just fine, I used Bourns instead which are a bit larger).
• J1: 24-pin ATX connector.
• JP1, JP2, JP3, JP4, JP5, JP6: 5-pin headers, male or female as you prefer.
• JP7: 3-pin header (voltmeter output).
• LED1, LED2, LED3, LED4, LED5, LED6, LED7: 0805 SMDs, choose the color you want but make sure to use appropriate resistors. You may not want full brightness and sure enough you don’t want magic smoke.
• R1, R3, R4, R5, R7: 3.3K ohm, 0805.
• R2: 330 ohm, 0805 (value may change – double check LM317 voltages or calculate your own).
• R8: 10k ohm, 0805.
• R9: 9/10W power resistor, not needed in my case.
• R6: 1.2k ohm, 0805.
• R10, R15: 43k ohm, 0805.
• R12, R14, R17, R19: 51k ohm, 0805.
• R11, R16: 75k ohm, 0805.
• T1, T2, T3, T4, T5, T6: binding posts with 4mm hole. You may want some red ones for the positive lines and a black one for GND.
• U1: LM-317, through hole.
• U2: TPS2513 from Texas Instruments. If you don’t have it, install resistors R10-R19 for the same functionality (not both!).
• VR1: 2k ohm, PCB mount potentiometer, 9mm (click)
• X1, X2: USB female connectors, through hole.
• SW1: 8x8mm pushbutton (got mine from Tayda.)

I bought all of my components from Tayda Electronics, except for the ATX connector and the PTC fuses (check Sparkfun or eBay!)

Time for some pictures:

And here’s a fully assembled one (terrible soldering on fuses and LM317 because I recycled them from a previous build):

PCBs will be available in the store and on Tindie soon.

Cheers!

I soon downloaded the ESP uploader and after reading some Lua docs (and finding out some weird things such as that the “not equal” operator is actually “~=” ) I started writing my own code for the board.

Writing and uploading software to the board is easy and fast. The only concern is that after flashing the NoceMCU firmware you are not left with a lot of memory available.

So I wrote a NodeMCU library (they call them modules) for the TI HDC1000. The code has been merged to the dev branch of the nodemcu firmware and it should go to the master soon, but I’ve set up a repo too (click!).

Download and upload the library

Click here to download the latest library.

You then need to connect to your ESP8266 dev board and upload the “HDC1000.lua” file to it. This is pretty straightforward using ESPlorer.

Setup your sensor

First, require it:

HDC1000 = require("HDC1000")

Then, initialize it:

HDC1000.init(sda, scl, drdyn)

If you don’t want to use the DRDYn pin, set it to false: a 20ms delay will be automatically set after each read request.

HDC1000.init(sda, scl, false)

Configure it:

HDC1000.config()

Default options set the address to 0x40 and enable both temperature and humidity readings at 14-bit resolution, with the integrated heater on. You can change them by initializing your sensor like this:

HDC1000.config(address, resolution, heater);

“resolution” can be set to 14 bits for both temperature and humidity (0x00 – default) 11 bits for temperature (0x40), 11 bits for humidity (0x01), 8 bits for humidity (0x20) “heater” can be set to ON (0x20 – default) or OFF (0x00)

Read some values

You can read temperature and humidity by using the following commands:

temperature = HDC1000.getTemp()

in Celsius degrees.

humidity = HDC1000.getHumi()

in %RH.

Check your battery

The following code returns true if the battery voltage is <2.8V, false otherwise.

isDead = HDC1000.batteryDead();

Complete example code

HDC1000 = require("HDC1000")

sda = 1
scl = 2
drdyn = false

HDC1000.init(sda, scl, drdyn)
HDC1000.config() -- default values are used if called with no arguments. prototype is config(address, resolution, heater)

print(string.format("Temperature: %.2f °C\nHumidity: %.2f %%", HDC1000.getTemp(), HDC1000.getHumi()))

HDC1000 = nil
package.loaded["HDC1000"]=nil

Some of the peculiar characteristics of this chip are that it has a DRDYn pin which goes low any time there is a new reading from the chip (so you can precisely time your requests) and that the sensor is located on the bottom of the IC, so that it’s not exposed to dust and other agents that may false the readings. Also, it has an integrated heater that can remove humidity from the sensor.

So I developed a very small breakout board for this chip as well as an Arduino library (yay, my first one! raspberryPi and nodemcu might come next).

The breakout boards.

I learned quite a lot about PCB design and soldering, effectively putting my new hot air station to good use.

The boards were again fulfilled by DirtyPCBs, perfect for this kind of small projects.

So here are the pictures of my board…

..and here are the features:

• Address selection jumpers: ADR0 and ADR1 are tied to GND by default but you can jump them to VCC in order to change the address of your sensor (default:0x40).
• I2C pull-ups to VCC for SDA, SCL and DRDYn. If you don’t want to use the latter, just don’t solder the resistor and leave it floating.
• 3-5V input, logic 5V tolerant (3.3V recommended).

Parts list:

• IC1: HDC1000 sensor, you can’t really go wrong with the package since, sadly, it’s the only one.
• R1,R2: 4.7k-10k ohm, 0805 package. I2C pull-up resistors.
• R3: 10k ohm, 0805 package. Pull-up resistor to VCC, for the DRDYN pin. Leave the pin floating if not used.
• R4, R5: 10k ohm, pull-down resistors to GND for address selection.
• C1: 0.1uF cap, 0805 package.
• JP1: 0.1″, 5-pin headers.

The board is 1.6×1.6 centimeters, and soldering that BGA chip (1.6×2 millimeters) wasn’t really that hard! I actually struggled more with the resistors, maybe because I used my ugly and huge 60W iron.

Here’s what I found works best:

1. Solder the components in this order: resistors, IC, capacitor (on the back of the board), pin headers. If you do it any other way you will have trouble balancing the board, I found it the hard way.
2. Apply a small quantity of flux on the pads (not on the middle of them, as it’s where the sensor lies..) – I used a flux pen.
3. Place the IC on the pads without pre-tinning anything, and fire up your heatgun.
4. If you aligned the chip correctly it will begin to stick to the pads by itself and you shouldn’t have to touch it anymore.

Of course you can do this with a reflow oven but using an hot-air gun it took me less than 3 minutes, for just the IC. You can’t solder this with a regular iron.

Note: the breakout boards should also be compatible with the HDC1008, but I haven’t tested it yet.

Now the best part…

The Arduino library.

Yesterday was a firsts day! (is this even remotely correct?) I soldered my first BGA and wrote my first Arduino library. I don’t think it’s quality code (there could be a lot to improve – should you feel compelled to do so, it’s on Github) but I tried to learn from both tutorials on the Arduino website and other libraries written by Ladyada and Seeedstudio.

How it works:

Just download (click!) and #include the library, declare your HDC1000 object and call the begin() function.

#include <Wire.h>
#include <HDC1000.h>

HDC1000 mySensor;


void setup(){
    mySensor.begin();
}

By default, the library is configured to enable both temperature and humidity readings, at 14-bit resolution, with the heater on. Also, the default address is 0x40. Should you want to change these features, you can declare your object like this (all the possible options are in the .h file – also check out the datasheet):

UPDATE 07/03/15: You can now use the DRDYn pin, which is pulled low by the chip itself when a new measurement is ready. It is off by default (drdyn_pin is set to -1).

HDC1000 mySensor(addr, drdyn_pin);

void setup(){
    mySensor.begin(HDC1000_BOTH_TEMP_HUMI, HDC1000_TEMP_11BIT, HDC1000_HEAT_OFF);
}

By default, the sensor outputs temperature and humidity readings in a 14-bit format. Fortunately, the library automagically converts them into Celsius degrees (sorry, Americans!) and %. You can access them like this:

double temperature = mySensor.getTemp();
double humidity = mySensor.getHumi();

You can also access raw values using the getRawTemp() and getRawHumi() methods (which return uint16_t values).

One nifty feature of the HDC1000 is that it can detect if the battery that’s powering it is nearly flat.

uint8_t dead = mySensor.battery(); //returns 1 if voltage < 2.8V, 0 otherwise.

The more tech-savvy of you can also read the registers’ configuration:

uint16_t config = mySensor.readConfig(); //returns a 16-bit value: last 8 bits are always zero and leading zeros are not displayed

Full, super-basic sketch:

#include <Wire.h>
#include <HDC1000.h>

HDC1000 mySensor;
//HDC1000 mySensor(addr, drdyn_pin) &lt;--- you can change default options if you want.

void setup(){
  Serial.begin(9600);
  mySensor.begin();
}

void loop(){
  Serial.print("Temperature: ");     //too bad the Arduino version of sprintf  
  Serial.print(mySensor.getTemp());  //doesn't support floats,
  Serial.print("C, Humidity: ");     //I hate Serial.print().
  Serial.print(mySensor.getHumi());
  Serial.println("%");
  delay(1000);
}

Sadly, I haven’t implemented the DRDYn pin yet, so I’m using a 20ms delay before reading the next value. I know that you can get the two readings at once (I send two separate requests to the chip) but I felt that there was no need to add another function to the library since you’d have to call two of them anyway.

As usual, leftovers (PCBs only!) are available in the store and on Tindie as soon as I get them approved. Design files on Github.

Let me know what you think – happy making!

I needed a small, fast and reliable multi-voltage level translator (mainly for connecting ESP8266 boards to the Arduino, got tired of resistor networks pretty quickly) so I built a breakout board for TI’s LSF0204(D).

Datasheet and info here.

The LSF0204 is a nice little chip. It can translate up to 4 signals to and from the following values:

1.0 V ↔ 1.8/2.5/3.3/5 V.

1.2 V ↔ 1.8/2.5/3.3/5 V.

1.8 V ↔ 2.5/3.3/5 V.

2.5 V ↔ 3.3/5 V.

3.3 V ↔ 5 V.

Here’s a picture of the board design:

It’s very easy to use: connect the reference voltages to VA (1.0-4.5V) and VB (1.8-5.5V), and your signals to A1/2/3/4 or B1/2/3/4. It will translate and output them to the opposite A or B pins.

Features and parts list

• Compatible with both LSF0204 (short jumper) and LSF0204D (solder/short the resistor between the “4” pins).
• Decoupling caps on both voltage lines.
• Optional I2C pull-up resistors (on the back of the board) connected to VA and VB.
• As small as possible! Just 1.6 x 1.6cm!

Parts list:

• U1: LSF0204(D) IC, TSSOP-14 package.
• C1,C2: 0.1uF 0805 package.
• R1-R8: 4.7k-10k ohm, 0805 package (I2C pull-ups, optional).
• R9: 10k ohm, 0805 package. Pull-down resistor to GND, for LSF0204D: the EN pin is active low.
• SJ1: solder jumper to VA, connect for LSF0204 (non-D): the EN pin is active high.

Pictures!

And here’s a couple of picture of some of the boards I received, printed by DirtyPCBs. Awesome service! Also, the black soldermask rocks.

It was also my first try at panelizing and I can say it worked pretty well!

Here a fully assembled one.  The chip is pretty small but it was easy to solder with the help of a liquid flux pen and my new Yihua-858D hot air station. Don’t worry, you can solder it with a regular iron too!

As usual, leftovers (PCBs only!) are available in the store and on Tindie, design files on GitHub.

Thanks for reading!

13/07/2015: PCBs of the new version have arrived. Blog post and store link!

30/06/2015: New version released, x20 PCBs printed and coming in the mail. New source files and details on GitHub – available for sale in a couple of weeks.

13/11/14: Eagle files have been uploaded, you can find the link at the bottom. Thank you for your interest!

Many people over the internet have already found out the usefulness of having an ATX PSU, often salvaged from old computers, on their bench. It can be quite easily converted into a lab bench power supply (owners of a real one, please don’t kill me).

There are lots of videos on how to add binding posts to your PSU and how not to, but I didn’t like any of these solutions. I tried the first one, but my power supply was so small and tightly packed that wires and binding posts wouldn’t fit right in it.

I then came across Sparkfun’s </a>and Dangerous Prototypes’ ATX breakouts. While I didn’t like the Sparkfun one, the one from Dangerous Prototypes convinced me a bit more.

Yet, I felt like it lacked some features I needed. I wanted some USB ports to power my rPi and charge my Nexus 5, and an adjustable voltage output. Furthermore, my PSU had a 24-pin ATX connector.

While I still consider myself a beginner in the enormous world of electronics, I decided to look up some guides on how to design a PCB (this time I’ve gotta thank you, Sparkfun! Both yours and Adafruit’s libraries and tutorials rock!) and have a try at it.

Fast forward some days later, my very own ATX breakout board was born.

Yes, it’s heavily based on the Dangerous Prototypes’ one, and I must thank them for this. I wouldn’t have been able to make one without them making theirs 🙂

The original board was 15 x 5cm and in my opinion had a much better design (the pot and 1 USB were on the front), but I resized it to 10x10cm in order to halve PCB manufacturing costs.

As I said a few lines up, it’s my first PCB so comments and feedback are welcome, if not encouraged.

These are the features I packed into it:

• It has a 24-pin ATX connector.
• Voltage lines are all broken out individually on binding posts.
• LM317-based voltage regulator. Using a 300 ohm resistor and a 2K ohm potentiometer, voltage range is 1.25-9V.
• 2 USB ports based on the TPS2513 from Texas Instruments. They can automatically detect what device is connected and adjust resistance on D+ and D- lines as needed. This means full compatibility and maximum charging speed on both Apple and Android devices. One of them is connected to 5v_STDBY, so that it works even when the PSU is off.
• Pretty much everything can be fused. I left -12V out because it can only carry low amounts of current on most PSUs (mine is 500mA maximum).
• Breadboard pin headers so that voltage lines can be connected to a breadboard using jumper cables.
• Voltmeter headers in order to know the LM317 output voltage.
• There is room for a 9W power resistor is your PSU needs it to stabilize output voltages. You can connect it either to the 5v rail or to the 12v one by jumpering the corresponding pads.
• Status LEDs on fused lines and USBs so you can check if everything works fine.
• Screw holes for standoffs.
• Breaking Bad art because yeah, this is science, bitch.

And this is the list of components you’d need to build it. All SMD parts are 0805 or bigger, because 0603s are so small they get lost on my messy desk.

• C1, C3: 0.1uF 0805 SMD capacitors.
• C2: 1uF 0805 SMD capacitor.
• F1, F2, F3, F4, F5: 1812 SMD PTC resettable fuses. (Littelfuse ones should work just fine, I used Bourns instead which are a bit larger).
• J1: 24-pin ATX connector. I bought mine from Sparkfun but RS also sells them.
• JP1: 3-pin header (for voltmeter output)
• JP2: 6-pin header (for breadboard output, fused)
• LED1, LED2, LED3, LED4, LED5, LED6: 0805 SMDs, choose the color you want but make sure to use appropriate resistors. You may not want full brightness and sure you don’t want magic smoke.
• R1, R2, R11, R12, R15: 3.3K ohm, 0805.
• R3: 330 ohm, 0805 (value may change – double check LM317 voltages).
• R16: 10k ohm, 0805.
• R6: 9/10W power resistor, not needed in my case.
• R14: 1.2k ohm, 0805.
• T1, T2, T3, T4, T5, T6: binding posts with 4mm hole. You may want some red ones for the positive lines and a black one for GND.
• U1: LM-317, through hole. There should be enough space for a heatsink.
• U2: TPS2513 from Texas Instruments. If you don’t have them, look up the datasheet and solder appropriate resistors on D+ and D- pins of the USB ports.
• X1, X2: USB female connectors, through hole.

Resistor numbers are off, I know.

I tried to stick to PCB design rules and to minimize the number of vias but I’m not sure I like the way I traced traces (:D). I made them as thick as possible, without diving into maths or trace width calculators, but they should be enough for most applications.

After the boards arrived, I noticed a small issue: a connection from R3 to C2 was missing. The fix was quick and easy and I soldered a little piece of a component between the two pads of all my PCBs (excluding my test one, pictured from now on).

This is how the board looks with all components soldered on:

And here it is up and running, charging my Nexus 5 at full speed. It also charges my iPad just fine.

Standoffs have yet to come in and I’m still figuring out whether I need the power resistor or not. There is also a voltmeter attached to the board, very handy.

I’m looking for some feedback from more experienced users so I can improve this board, maybe by making another revision (the next one will undoubtedly have a switching regulator!), and learn a bit more about PCB design. I am pretty happy with my first try though.

I made 10 pieces of this PCB, which was the MOQ. I’m keeping 2 of them but I need to get rid of the other 8. If you want one, just leave a message down here and you can get one for 5€ (PCB only), which is just a bit more than the cost for shipping worldwide.

Thanks everybody!

EDIT: The response from the community has been great! There are no more PCBs left. I’m planning on making another revision and Eagle files / Schematics are coming by the end of the week.

UPDATE: Eagle files available here. The missing connection has been fixed and traces widened. Breaking Bad references removed. Parts numbering is more correct now, yet I still need to update the main post. GitHub repo here.