CT406 : proximity and light sensor on MotoG

The CT406 module is both an Ambient Light Sensor (ALS) and a proximity sensor.

There are not much documentation on this product so here is what i understood from my research:

the above picture is a macro-picture of the ALS/prox sensor of my MotoG (MotoE has exact same module, but on the left side of the screen)

• On the left we can see a InfraRed LED (near IR range since we can see a little reddish light in the dark, but my camera catches part of IR spectrum and displays some kind of purple)
• In the middle there is a black spacer.
• On the right this looks like to be the sensor itself (from here, we know that the sensor is only an ALS that works as proximity sensor when coupled to an external IR-LED)

Here is the TAOS TSL277x chip that seems to be the base of the CT406.
TAOS (Texas Advanced Optoelectronic Solutions) brand is now known as ams.

Superposing my picture and that artwork: Pretty identical, right?

The pins are arranged this way (scheme is rotated 90° right compared to my picture):

How does the proximity sensor works? IR reflection...

The IR-LED emits Red-InfraRed lights and the right part detects if it is reflected or not (reflected == near; non-reflected == far)

To test this, it would be nice to use an external IR-LED and hide the embedded one to see if the sensor still say "far" when under IR light and "near" when IR light is turned OFF.

On our devices, the ALS sensor can only response a "high/low" output, but without the glass panel (that filter some IR) and a reworked program it could be used as presence detection (longuer range) [Source]

How does the ALS sensor works? Wide range light detection, IR detection, and human sight.

The chip features 2 photodiodes (one responds to wide range light: ch0; the other only gets IR: ch1)

In the above diagram we see ch0 respond to light from 300 (near UV) to about 1000nm (IR)
Humans see light from 390nm to 700nm (about, this means from deep-blue/ultra-violet to deep red/infrared), 

Humans don't see IR, therefore, light emitted from 700 to 1000nm produces a response from the light sensor (ch0) but Humans are actually in the dark, that would scale up light intensity of the device screen for no "human understandable reason".

That's what the IR sensor (ch1) is used for: the chip calculates something like ch0-ch1= actual human visible light intensity. Actually this is more complicated than this [Source, page 8&9]
The ALS operations have for duty to calculate what a real human would see (so, a spectrum without IR) in order to light the screen at the right human friendly level.

Luxmeter ALS outputs Lux that are then used by the device

The ch0 could give directly the light intensity with no real calculation if the system was open (no glass, whatsoever), and if there were no IR sensor. [See more page 10]

Real Life How does it work inside the MotoG?

Basically, the CT406 contains the following components :

• a sensor that is made of 2 photodiodes, one is wide range and reacts to human visible spectrum + IR; the second one reacts to IR only.
• an Infrared Light Emitting Diode (IR-LED)

The light sensor "reacts" to visible spectrum by using the signal coming from the wide range photodiode minus the IR one.

The proximity sensor is basically the IR photodiode reacting to IR light emitted by the IR-LED and reflected by a near surface.

The module speaks to the device using i2c protocol.


Proximity sensor has two states : 

• near (what the devices call "3cm") and 
• far (what the device calls "100cm")

The ALS has the following working range: 

• 2 lux (the light intensity is lower than sensor threshold)
• 65535 lux (fully saturated)

"The device can saturate if the light is brighter than can be accumulated with the light−to−frequency conversion. The full scale value for saturation will depend upon the integration time programmed into the device. In saturation, the device accumulates 1024 counts for each 2.72 ms of integration time programmed. For each ATIME programmed, the maximum count (saturation level) is the lesser of (1024 * (256 − ATIME)) or 65,535."


This explains a few things about why the screen is not at the intended brightness level.

• If the light isn't a wide range one; like a "white LED" which is actually a blue led with phosphor coating == the blue shift will saturate the sensor despite the "real" (== human felt) brightness is much lower.
• If the light is PWM controlled == is being lighten ON/OFF at high frequency to get desired "global" intensity : it would saturate the sensor  regarding sampling.
• if the light is a fluorescent light (same as for PWM controlled ones)

CM12 and MotoG

First overview Tip and Tricks

Here are some things i found after playing a little with CM12-20150108 Nightly :


How to get root ?

1. Enable Dev settings (multiple tap on "Build Number" in /settings/about phone/)
2. Go to Dev settings
3. Root access : Change to Apps and ADB

How to get Terminal app back?

It is now disabled by default, simple enable it in Dev Settings by toggling "Local Terminal"

That's all for today folks!

This blog might be totally reworked in the coming months but i don't have much time at the moment...

MotoG : Pure CPU Benchmarks, the limits

To point out pure CPU Benchmark flaws, we'll observe how does a moto G (Falcon or Peregrine, this has no relevance) behaves with Linpack Benchmark when running on Stock 4.4.4 Motorola ROM or CM11-20141124-nightly (4.4.4).

We have seen previously that Linpack didn't use all cores and was limited to 3 threads in multi-thread benchmarking (when comparing s200 and s400 SoC).

Now, we will compare MFLOPS performance between two ROMs that has similar user experience (smoothness mostly)

Stock 4.4.4 Motorola ROM vs CM11

both @1190MHz, Interactive governor.

Stock Motorola features a nearly doubled score for both Single and Multi-Thread, but does that mean it is really better optimized?

• In a way, yes, CM11 is made to be compatible with most devices, so we encounter similar problem seen with Windows against iOS : 
• An OS that fits all against a fully optimized one made for a few specific hardware. Motorola obviously optimized their software to get the best of this great device
• If you compare with the MotoG vs MotoE test, you'll see that the MotoG running CM11 has lower results than MotoE running stock ROM ...

• On the other hand, that's not all a matter of optimization :
• CM11 features KSM, zRAM, and many things that use CPU cycles to compress memory (zRAM) or merging merge-able things (KSM) ==> this reduces CPU pure performance but increase multi-tasking ability.
• The war of versatility and customization against slickness and stability...
• Honestly i can't see difference in user-felt performances...

Actually, i don't see any issues by using CM11 as a daily driver on my XT1032 (Falcon), it is not because a Benchmark say something that it is true in "real life"...

• Don't use CM11 on Moto G if you want to show off with high CPU benchmark results ...
• Stock Motorola ROM is close enough to AOSP to be acceptable as daily driver
• Xposed helps you to get the best of stock ROM
• CM11 is great for end-user customization

The real conclusion is the following :

Don't trust Benchmarks as incontestable truth, they helps to compare devices and  ROMs, but never really tell you how good devices/ROMs are.

Moto G and Moto E : snapdragon 400 vs 200

Snapdragon 400 vs Snapdragon 200 based on msm8926/8226 vs msm8610

After we studied MFLOPS per MHz ...

It is now time to compare MotoE and MotoG:

Moto G and E features a Snapdragon 400 and 200 (respectively a Quad-core Cortex A7 @1.19GHz and a Dual-core Cortex A7 @1.19GHz)

Note that previous benchmarks were performed with ONDEMAND governor on CyangenMod11 ROM, but stock Moto ROM uses Interactive by default (i didn't expected that...) so the following has been made with interactive for both devices (needed to re-bench MotoG >_<)

to check above results are applicable despite governor modification : 

MFLOPS per governor on MotoG (Falcon, CM11) @1190MHz

No significant difference between ONDEMAND and Interactive governors for the specified test.

Moto G (Peregrine) vs Moto E (Condor) msm8926 vs msm8610

To improve accuracy, instead of using my Falcon (XT1032) running CM11, we will compare results obtained on a Peregrine (XT1039) running Stock Motorola ROM :

Both Benchmarks have been run on Motorola Stock 4.4.4 ROM on Moto G (Peregrine) and Moto E (Condor):

There is no differences between msm8226 (Falcon) and msm8926 (Peregrine) despite LTE capability of msm8926, that's why we will use a Peregrine for the following part.

MotoG (Peregrine) vs MotoE (Condor) @1190MHz, stock 4.4.4

We have quite similar results on Single Thread application for one simple reason, the number of cores does not have any impact. Since the clock speed is the same, the results are the one expected.

On Multi-thread the difference is quite huge between the quad-core and the dual-core, though we don't see a x2 ratio by doubling the cores number.

MFLOPS divided per the amount of cores

x/4 for msm8926 and x/2 for msm8610, Single Thread as control.

We should have observed a similar result between Single and Multi/nbCore...
Is the msm8926 really shitty at multithreading? i don't think so, looks more like if linpack or the system only uses 3 Threads...

If we apply a corrective divider (3 instead of 4) the results are perfect :

MFLOPS divided per the amount of threads used

x/3 for msm8926 and x/2 for msm8610, Single Thread as control.

Moto E (Condor) and Moto G (Peregrine or Falcon) should have similar performance in single threaded applications.

Though the 4 Cores may no be used at their full potential in some apps, multi-threaded applications should be better handled by the msm8926/8226 featured by moto G.

Moto G? or Moto E? Which one for What...

For moderate usage, Moto E is quite enough compared to Moto G : 

• It is not weaker on Single Threaded applications
• It has a smaller battery but both smaller CPU and half size Screen in pixels (960*540 vs 1280*720) will give it a great battery life.

Moto G is still the best quality/price in its category (prefer the Peregrine version and not the Moto G 2014 aka Titan)

• Multi-threaded applications will obviously run better on it
• The better Screen density improves user experience on long term usage
• A far better Camera...

A complete Moto G - Moto E versus is available on versus.com (note that Moto G Peregrine does not have 16GB of internal memory ... but only 8, and an SDcard slot.)

Installing Opera 26 and Adobe Flash Player? Pepper Flash!

After the Linux Mint 17.1 upgrade, why not trying Opera 26 ? (Opera had not been updated for Linux since Opera 12 before this new release)

Getting to the Opera Web Page and downloading the x64-only .deb :

Installing the deb package : (the package will seek for dependencies)

If you want Opera to get its updates with system updates, then :

Need Adobe Flash Player ?
What about using Pepper flash instead of Adobe oldies?

sudo apt-get install pepperflashplugin-nonfree

Restarting Opera, and we're done!

CPU Freq and Performances : Single and Multi Thread

Linpack Benchmarking for Moto G, Single and Multi-Threads...

Before we compare Moto G and E Snapdragon 400 and 200 (respectively a Quad-core Cortex A7 @1.19GHz and a Dual-core Cortex A7 @1.19GHz), let's see how the Moto G performs with ONDEMAND governor and increasing CPU Clock.

MFLOPS and CPU Clock speed On Moto G XT1032 aka Falcon, CM11

A MotoG XT1032, running CM11-20141124-NIGHTLY has been used for MFLOPS per MHz tests.

The CPU is downclocked at 787MHz, and then frequency is raised up to nominal Frequency that is 1190MHz. Here are Single and Multi-Thread MFLOPS results.

You can note that 998MHz had inconsistent results due to high standard deviation...

MFLOPS/MHz A closer look to the results

Multi-thread results raise quicker than Single Thread, let's explore this closer :

As we can see, 

• MFLOPS/MHz ratio does not increase much for Single Thread, but,
• For Multi-thread the ratio increases between 787 and 998MHz but then stagnates : This means that MFLOPS increases in a linear way as Frequency is raised.

This can be explained by the following fact : 

The OS needs some CPU cycles to stay ON, so under a certain frequency it conflicts with Linpack work and decreases performances more than expected.

Conclusion? As a conclusion, we can say that CPU clock increase is more effective on multi-threaded applications (in a quite linear manner) than on Single threaded ones.

2x5W Amplifier for mp3 player or line output (MK190) (part3)

Last update about the Audio-amplifier project,

While i was messing around to build a testing NAS with a Pentium D based set up (irrelevant to be used as a 24/7 NAS due to high power consumption of the platform...), i found an old 12Vcc/2.5A PSU from a broken external USB/Firewire HP DVD writer (that i had forgotten to own >_<).

What the DVD writer looked like ==> 

The wires were slightly damaged, so i simply re-soldered to the cable i previously made.

Here is the final result :

The Audio-amplifier project is now Closed and considered as finished. It is neither slick nor compact, but it's mine and works pretty well!