Thursday 27 August 2015

Level converters - How to safely connect an Arduino to a ESP8266 module

This is the companion blog article to my video on YouTube.
A second part with a practical application will follow.

Option 1: Bidirectional N-type Mosfet level shifter

This is my favourite "no worries" solution. These modules provide 4 bidirectional lines. Enough for most of my little projects and more than enough for a serial connection between an Arduino Uno and a ESP-01 module.

These level converters can be obtained for cheap from here.

Option 2: Voltage follower

Not bidirectional but also a very clean solution is this voltage follower. The output level follows the input signal but only to the point when it reaches the supply voltage. I.e. 3V in this case.

The popular 2n2222a transistors will serve the same purpose and can be bought here.

Option 3: Zener clamp

This is a great option if you want a reliable solution with a minimum of components. The Zener diode clamps down the voltage on the 3V side of the resistor. (Output signal shown in green here.)

Here is a link to a set of zener diodes.

Option 4; Voltage divider

By far the cheapest option for a quick hack. The classic voltage divider. It does not provide any additional protection against voltage surges, but where those are not to be expected, you'll easily get away with that simplest of circuits.
Resistors are dirt cheap and you should always have some available. Here is a very basic set.

Tuesday 18 August 2015

Problems on windows 2008R2 production server following August 2015 patches

As a followup to this post, two of the August 2015 updates apparently fix the same issue, causing problems on one of our servers.

While in July the patches were:
KB3067505 and KB3057154

This time it is:
KB3060716 and  KB3071756

With these patches installed, a hot folder mechanism refused to work more than  once. The actual mechanism behind it still remains in the dark at the moment. Looking at the security bulletins, the problem appears to center around a privilege escalation bug.

Removing these two patches brought everything back to normal.

Monday 10 August 2015

Windows 10 (nearly) broke my Intel 4 Series Express graphics adapter

After an otherwise smooth transition from windows 8.1 to  Win 10 on my Dell E6400, OpenGL applications stopped working.

Stellarium relies on OpenGL
My graphics adapter apparently does not support openGL any more. It is an:
"Intel 4 series Express Chipset Family" adapter that has gone out of active support for quite a while.

After some failures, I found a surprisingly simple solution:
This Win7 driver from the Intel download center installed without any issues and brought OpenGL back at an (for this system) acceptable speed.
OpenGL is back - and so are the stars.

While a slightly newer installer ( refused to run on Win10, this one ( did.
I will probably have to prevent windows from updating that driver in the future.

20150824 Adendum:
The sound output of the docking station wouldn't work either. Replacong the IDT audio driver with the standard high-definition audio driver fixed that.