Tag: android

In 2018, a tablet still isn’t a computer

Simone 1 Comment

What is a computer? That’s the title of one of the latests commercials about the iPad Pro.

In a nutshell, the designers show that the tablet has nothing to lose when compared to a computer.

I beg to differ. I was recently searching for a replacement for a laptop, and the tablet was an interesting candidate; but after research and first-hand testing, I’m confident to say a tablet is not a computer. They are two different products for two different use cases. Sure, a 1000€ Microsoft Surface can get close enough to a laptop, and also the iPad has some niceties that make it above average in many areas, but things get worse if we look at the much more widespread Android tablet, which is the worst offender here, even for devices with a 600€ price tag.

There are many things a Android tablet cannot do well or at all.

  • You cannot have two apps running at the same time reliably, as Android likes to kill them randomly. This is especially problematic if you’re using tools such as IRC or SSH which happen to use connection-oriented protocols.
  • Physical keyboards aren’t remappable without rooting. For example the Escape key closes all applications and there is no way to disable it. (90% of keyboard shortcuts do work though.)
  • Support for external peripherals is almost non existing. While all Android devices have a USB port, this can’t be used for USB devices such as USB-to-ethernet adapters or USB-to-HDMI. So, no wired networks and no external monitors are allowed. If you need those, you’ll have to do some research, as support is extremely spotty (Samsung and Apple are among the best here).
  • Drawing is impossible as the latency is huge, especially on bigger screens. The only possibility here is to get a tablet that has support for an active pen (that currently is available only on the top tier ones). Also the pen itself is, again, expensive.
  • Filesystem support is cumbersome. Try to download a file in a new directory and then move it somewhere else. Or try to forward an email with an attachment on the iPhone.
  • Gaming on a tablet is a sub-par experience, as mobile games are not at the same level as mediocre PC indie games.

On the other hand, I don’t mean tablets are useless; they are fit for different purposes. Even many laptops have disadvantages with respect to a tablet:

  • Few laptops support SIM cards.
  • Laptop cameras aren’t as advanced as mobile ones, and a laptop anyway can’t easily take a picture of what it’s behind it.
  • Few laptops are touch-enabled.
  • “Flip” or “Transformer” designs are rare. The keyboard is a burden if you just want to watch YouTube. This basically makes a laptop much less portable.
  • Laptops just aren’t socially fit sometimes, you’ll look weird if you bring one at the beach.
  • Many mobile apps are designed around portability: maps, touristic informations, public transports, and so on. Unfortunately many of them aren’t available for all platforms; if you’re used to a certain app on your phone, you might need something different on your laptop.
  • Mobile apps often offer background services which are less resource-intensive than keeping tens of Chrome tabs open.

So, there are pro and cons on both sides, as they’re basically two different products with a slight overlap in functionality. Tablets still excel at entertainment, but laptops are still the most versatile and productive.
You should understand your use case before deciding for the one or the other. I hope this list helps!

 

Bluetooth low-energy temperature beacon using the nRF24L01: cheap and compatible with existing smartphone apps!

Simone 8 Comments

The reason I did this project is because I have a slight overheating issue in a server room; I was wondering if there would be some way to check another room’s temperature from my desk. That’s how I came up with a “wireless thermometer” that can send readings to my Android phone, and my colleagues can use it too!

You might have heard about the nRF24L01: it is a cheap (0.80€) radio frequency module that, back in 2013, Dmitry Grinberg was able to use to “fake” a BTLE beacon. Real Bluetooth 4.0 modules are, nowadays, about 5€ each.

I wondered if I could use it to make a BTLE compatible temperature beacon. Turns out there are 3 major BTLE beacon protocols: iBeacon (by Apple), Eddystone (by Google), and AltBeacon (by Radius Networks). And well, none of them can be emulated with the nRF24L01, since it is only able to send a 16-byte payload (among other limitations), and all three of those protocols require bigger PDUs.

BUT!!! Although I didn’t find a name for it, Nordic Semiconductors Bluetooth ICs (namely the nRF8001 and nRF51822) have their own protocol they use to send telemetry data (which means: temperature, battery level and device ID); turns out this protocol is simple enough to be emulated by the nRF24L01 as well, although with some limitations. They also are so nice to distribute a suite of Android and iOS apps to work with them; the most relevant apps are nRF Master Control Panel (useful for debugging BTLE devices) and nRF Temp 2.0 (a temperature logger; I think it was meant to track device overheating, but hey). You can also download the source code from the app page!

wpid-wp-1444076649110.jpeg  wpid-wp-1444076692964.jpeg
However, the temperature in my room is quite boring, as shown from those screenshots of Nordic Semiconductors apps. (nRF Master Control Panel on the left, nRF Temp 2.0 on the right).

The temperature beacon hardware is very simple. Just wire up your microcontroller to a nRF24L01 and a temperature sensor of your choice (I used a DHT11 I had lying around).

wpid-wp-1444076633700.jpegIt’s more about how you wire them up, I guess.

 rf24-pin
(fabacademy.org)

  1.  GND -> GND on the Arduino
  2. VCC -> 3.3v on the Arduino
  3. CE -> PIN 9 (see below)
  4. CSN -> PIN 10 (see below)
  5. SCK -> PIN 13 on the Arduino Uno
  6. MOSI -> PIN 11 on the Arduino Uno
  7. MISO -> PIN 12 on the Arduino Uno
  8. IRQ -> not used

Be especially careful about the power pin: altough the nRF24L01 can work with your 5v Arduino, you must power it at 3.3v!

While SCK/MOSI/MISO are pretty much wired to 13-11-12 pins in order to use SPI, CE and CSN can be moved to a pin of your choice.

About the DHT11, just wire its output pin to A0, and the other two to ground/+5v.

On the software side, I did a couple modifications on floe’s BTLE library to allow mimicking of the nRF8001 and nRF51822; you can find the BTLE library here. With this library, you can now create your temperature beacon. (Notice I used pins 9 and 10 as CE and CSN, as mentioned previously).

Did you know? Most Arduinos have an onboard temperature sensor! The reasoning behind this probably is that a device malfunction would overheat it. Unfortunately this can’t be easily used as an ambient temperature sensor, because the chip temperature is widely influenced by its heat dissipation. That’s why I used a DHT11. (You can read more about this on Arduino Playground here).

Among other limitations, this setup is not able to use more than 3 of the 40 BT 4.0 channels, and broadcast a name longer than 8 characters (remember that 16 byte limit?). I’m pretty sure it could be used to broadcast the battery level as well.

Sadly, it does not seem somebody has thought of writing a standard protocol for broadcasting some other non-temperature parameter (atmosphere pressure, light, noise level, etc). To a certain extent, nRF Master Control Panel can be used to receive arbitrary data from the Arduino (as float or as integer value), but it’s not suitable for logging and combined with the 16 byte limit it’s quite limited (BT also has a 2 bytes overhead for every field you want to send, hence: 8 bytes device name + 4 bytes temperature + 2*2 bytes of overhead = 16 bytes). If I’m wrong, let me know!

I hope you enjoyed this article!