Topic: Making

The wi_ther Environmental Sensor (Revision A) Is Complete

2016-08-06 11:23 - Making

The prototype and final wi_ther environmental sensor.

My new boards arrived and I've assembled the first (totally working!) "wi_ther" environmental sensor. The prototype, which I've posted about before, and was supposed to be the final version, is on the left while the new board is on the right.

The new board is larger, to put more space between the hot WiFi/controller chip and the three sensors, which are closer to the proper USB connector, rather than the on-PCB fingers. I got the connector a tiny bit wrong, I had to cut off a bit of the board to make it fit properly, since I put too much empty space around the holes for it to mount to.

You can see three internal cut out slots to help break any thermal transfer from the controller to the part of the board where the sensors are. The surface mount temperature sensor also has extra cutouts around it, and the two other sensors have big slots cut out beneath them, which is nearly invisible in this picture.

I'm still finalizing how I want the software to work. For now this system is running an HTTP server, which can be polled. I've also considered letting it run as an HTTP client, periodically pushing the data out. It might be nicest for it to run as an independent system, keeping a buffer of historical data in memory, in case anything causes my normal system to miss then that data can be retrieved thanks to the independent storage. But for now, it's time to stress test it and verify whether my thermal design for this version helps the sensors provide accurate data. (Early signs are good! In the few minutes it's taken me to type up this post, the reading has remained flat, so they haven't been heated by the processor!)

Wireless Weather Sensor Prototype

2016-07-20 21:17 - Making

First complete working prototype of my wireless weather station.

Here's a picture of the just completed first prototype for my wireless weather sensor. I'm upgrading the temperature sensor design because I didn't do a great job with it. I got it to the point that it's barely functional, learned some things, and so now it's time for round two.

I've still got the DS75 temperature sensor I started with. It's at the top middle of the picture, the tiny chip on the larger green board. Moving slightly counterclockwise, behind a forest of wires, is a black box: that's an AM2320 sensor which does both temperature and humidity. Continuing clockwise from there on a purple breakout board is a BMP280 barometric pressure sensor, which also does temperature to boot.

All three of these chips speak the same I2C communication protocol, so it's just the two orange wires from the big board at the bottom (a clone NodeMCU) that connects to all of them, as I2C is a shared bus. Now that I've got it working, I know for certain that I understand all three chips and how to wire them up. And get data out:

Reading at 874742: AMT=80.06; AMH=49.00; BMT=82.83; BMP=101974.61; DST=81.05

They only mostly agree about the temperature, with a drift of a couple degrees between them. In practice I'll probably take the average (mean) of all three readings. I've got plans for a PCB to put all this on. It will be bigger than the previous one, and more carefully designed, with internal slots to make sure the heat from the WiFi/controller chip doesn't reach out to foul the temperature sensors' readings, and a real USB connector (just for power) rather than trying to use the PCB itself for that when it's too thin to do that job well.

Wireless Temperature Sensor Complete

2016-06-29 23:50 - Making

I've "finished" my wireless temperature sensor project. At least the first version.

The final tests on a breadboard. In situ, front view. In situ, rear view.

The first picture here is the final test before "done", on a breadboard. It's assembled and plugged in there. Look at the middle picture and you can just see (U4) the first mistake. The power regulator isn't the size I thought it was. I got lucky that I could force the smaller chip to line up just good enough to use anyway. Then on the breadboard I realized the second design mistake. I knew of the idea of designing thermal relief into a board like this, with temperature sensor included. I neglected to do so, however. Turns out the chip running the WiFi pushes the temperature on the board up around ten degrees above ambient, and with the (surface mount) temperature sensor (U3, top right of the mostly-in-focus middle picture) also right on that board, under an inch away, it doesn't give the sort of readings I want.

Luckily the next day the pair of AM2302 sensors I ordered arrived in the mail. These are the same as the DHT22, which is compatible with the DHT11. I've had some DHT11 units for a while — they're awful quality (for this application), but they do have a passable humidity sensor. And I had nothing else to do with them, so I left a place to put one in. The DHT22/AM2302 sensors are much better for this project. And they're not surface mount, so they won't be corrupted (as much?) by the heat of the processor/WiFi work. It's the white plastic box visible in all three pictures (most obviously in the last one).

The new sensor was pretty easy to hook up to the dev board (bottom right of the first picture), which is a cheap NodeMcu knockoff. But I couldn't get it to work in my board. Turns out I selected an arbitrary pin (11, GPIO9) based on proximity/convenience on the board. That pin won't work for this application (argh!), and I didn't test that before getting the board made. So, as you can just see in the last picture, the data pin is lifted, extended, and run over to one of the extra GPIO breakout points I included "just in case" (phew!) which works.

So far it's been plugged in since last night and it's happily answering my queries for data. I'm running a quick test to see what sort of data it produces overnight. But overall, it looks to be in a good enough state to begin using.

This is my first ESP8266 project, to mixed results. It's really convenient to have a programmable WiFi capable microcontroller, but programming is a bit of a pain, all the networking smarts bulk up the programs a lot, so they take a while to upload. Plus it's a bit of a dance to get it in the right mode to accept the programming. For my board, I ended up relying on the second UART port for diagnostic output, I couldn't get reliable data out of the primary one. If I have another small project where WiFi interaction would be useful, I'll probably give it another try but I'll be cautious.

That second project might be a second version of this very project. I'd like more sensors so I could know, for example, how much (if any) difference there is in temperature in various parts of my apartment, especially "upstairs" in the sleeping loft. That's why I made it wireless: so it's easy to put wherever I want, as long as I have power available to run it. I can fix the mistakes I know of, and perhaps try again with a new better version.

Weekend Project: Beginnings of a Wireless Temperature Sensor

2016-06-05 18:37 - Making

I've had computerized logging of temperature, indoor and outdoor, since I lived in my previous apartment. Both the heat and A/C there was electric, which I paid for. With a clunky old unit. So I hooked temperature sensors to the server I ran all day anyway, and put a relay in front of the HVAC unit to create a simple thermostat. It's fun information to have, so I've kept it.

My logged temperatures since 2009.

But they sensors are clunky wired units with some nasty quirks; for example on Friday it said the temperature inside remained exactly 77.1 degrees for about 20 hours straight. There are a couple spots that it will get "stuck" like that, and it limits the possibilities for me to lay things out (server + wire must reach out the window to keep outdoor data).

My temperature sensor project in its breadboard infancy stage.

I've meant for quite some time to build something better. I have an esp8266 wireless unit bought on impulse lying around, at bottom left of the image besides this text. I've also got some DHT11 sensors I could hook up to it. Those are the little blue boxes in the top right, three in the tray they came in and one actively hooked up. And working!

But the DHT11 turns out to be awful. It only gives 1 degree Celsius resolution, so about two degrees Fahrenheit; I'd prefer something like 0.1 degree F resolution. It also does humidity which is nice, but with similarly lackluster abilities.

In my last electronics parts order I grabbed a few DS75 chips, which can do temperature to 0.0625°C resolution. It's sitting on the green board in the bottom right of the picture; next thing to do is to try to talk to it!

Update, on the 6th: I've got the DS75 hooked up and working and I can indeed get my 0.1°F or so readings out of it. I know for sure because I can watch it heat up a bit as I touch it with my finger, and cool off when I let go.

WiFi Add-on for Rapberry Pi Zero: Zero Pants

2016-05-16 21:19 - Making

I recently became the proud owner of a Raspberry Pi Zero. An amazing little gadget for its $5 price point! But as a result the features are a bit spare. When I found this RPi WiFi project on Hackaday I was hooked, I needed to have one. But it's not available, yet.

My Zero Pants board to add WiFi to the Raspberry Pi Zero.

The original project is more ambitious than my adaptation of it. I only put the ESP module and a breakout for (power and) serial data. A stacking header mates with male header pins attached to the Zero, and voila! The original seemed to be called "WiFi Pants", with my simpler version intended to work with the Pi Zero, I chose to call mine "Zero Pants".

There's just one caveat: it doesn't start at boot. I'm pretty confident this is because I'm using the ESP-12-E module, which is set up with embedded flash and program to run. So I have to do the GPIO twiddle in step 10 of the instructions. But that causes a kernel panic. Actually what I need to do, so I have for now as a script file, is:

rmmod esp8089
echo 0 > /sys/class/gpio/export
echo low > /sys/class/gpio/gpio0/direction
echo in > /sys/class/gpio/gpio0/direction

Remove the kernel module first, then toggle the GPIO pin to cause the ESP to restart. The module automatically reloads itself, and if you have a valid wpa_supplicant.conf set up, it connects in just a few moments.

Plus I needed to patch the esp8089 module to get it to compile for the recent kernel I got by following the instructions. (As mentioned in the comments.) But hey, it was a nice fun small project!

I ended up not installing either of the LEDs in this, the second module that I assembled. I got something wrong so the power LED was unnecessarily bright, and the "init" LED did indeed blink correctly to let me know the GPIO was twiddled. But it's normally high, so stays on the whole time, and also terribly dim, because it's being powered through the (I assume?) processor's internal pullup resistor. So no need to keep that!

Nevo C2 Remote Control - Reverse Engineering - Part 3

2016-05-08 16:39 - Making

After quite a delay I'm continuing this series of posts.

I've learned that Samsung's SAM8 line of microcontrollers is based on the Zilog Z8:

Historically, the SAM8 and SAM88 CPUs that are the core of the S3 Family were based on Zilog’s efficient Z8 architecture. For Zilog to introduce the S3 Family is simply a natural evolution culminating in a cooperative agreement between IXYS and Samsung.

And that Zilog has purchased this line from Samsung to bring the product full circle:

IXYS Corporation, parent company of legacy and legendary microcontroller manufacturer Zilog, has entered into an agreement to purchase 4-bit and 8-bit Flash microcontroller product lines from South Korean semiconductor manufacturer Samsung Electronics for $50 Million.

This nugget of info helped me find the S3 Embedded Flash Serial Programming document (mirrored at and locally), which at first seemed very promising. The best I could find from the datasheet was vague references to "tool mode" which the TEST pin could set, but not whether it's active high or low, and also a NRESET pin with no polarity/value indication, and SDAT/SCLK which sounds like I2C. (The N in NRESET implies active low, and some vague wording implies active high for TEST, but that's not enough to go on by itself.) And no data about the protocol. But this S3 document from Zilog mentions pins with nearly identical names, has much more clear wording about the Reset and Test pins, and specifies the protocol to talk over the data line!

Unfortunately all my attempts to whip up something to talk to this chip with that protocol have failed. The Arduino is terribly easy to work with, but I've only got 5V modules, so I tried working with the 3V STM32 board I have instead. I might have been tripped up by the dual-direction data line (output at first to specify the operation, then input). Either way, I can't get the chip to respond.

Next up is the J6 header which just has two power pins and two UART interfaces. It took a little digging, but I found that UART1 spits out some data at power up, at 38400 N81; here's several repetitions:

00000000  00 00 55 49 42 30 01 0b  00 00 55 49 42 30 01 18  |..UIB0....UIB0..|
00000010  00 00 00 55 49 42 30 01  0b 00 00 55 49 42 30 01  |...UIB0....UIB0.|
00000020  18 00 00 00 55 49 42 30  01 0b 00 00 55 49 42 30  |....UIB0....UIB0|

By watching in my logic analyzer, I can see an 0x00, followed by an 8ms delay, then the 0x00 UIB0 0x01 0x0b, a 10ms delay, an 0x00, another 8ms delay, then the 0x00 UIB0 0x01 0x18. There's a clear pattern here, but I can't interpret the data. With the guts of the remote tacked down to the breadboard I can hardly interact with it. When I move it the backlight lights up, but I see no serial traffic. I can get to a few of the hard buttons beside the display, and they also have no effect.

The JTAG interface remains. But it will remain a topic for another day, as I've got learning to do before I have a chance of making progress.

Nevo C2 Remote Control - Reverse Engineering - Part 2

2016-03-09 22:14 - Making

For context see part 1, which has pictures and descriptions of the chips I'm referencing.

The important bits are two microcontrollers: one ARM made by ST, ("Chip 1") one 8-bit made by Samsung ("Chip 7"). I'll be referring to them as ARM and SAM8, respectively. Plus three connectors. There's J6 and J8, both close to the SAM8, both two by three standard 0.1" pitch headers, unpopulated. Then a completely unlabeled two by four arrangement of rectangular pads next to the batteries, far from any chips. I'm calling this one JX, for either eXtra or eXternal -- this one is accessible without disassembling the remote at all, just by opening the battery compartment. I've figured out what these all do, so let's share!


Just like J8 to come pin one is clearly marked as the singular square pad of the six, plus the notch on the silkscreen layout. Orient yourself so it's top left and I've chosen to label the pins counter-clockwise like a standard IC package. All of these are connected through to the ARM controller, like so:

J6 PinARM Pin
1P1.3 UART2_RX
2P1.5 UART2_TX
5P1.0 UART1_TX
6P1.1 UART1_RX

I was quite confused for a while at the selection (port 1, pins 0 1 3 5, skipping 2 and 4??) for a while until I found, on pin 47 of its data sheet the alternate functions available on those pins, and the pattern seemed clear. I'm mildly surprised to see two UARTs broken out, perhaps the software dedicates one to sending and one to receiving, or command/debugging output, or some other combo? Or perhaps one is unused, "just in case" design. Certainly it will be interesting to check, but I doubt it will be much use on its own.


Also located just next to the SAM8, this is clearly a programming header for it:

J8 PinSAM8 Pin

Unfortunately data on this line of micros looks sparse. I can see these pin names, and a bare description of their function, in the data sheet, and it makes sense as a synchronous serial channel, and the TEST/nRESET pins to force it into programming mode. But what protocol goes over this channel? I surely don't know. The data sheet also has a surprising list of development tools listed, but none of them are common things. I could only find concrete evidence of one, a storefront with no price listed, which makes me think "If you have to ask how much it costs, you can't afford it." Certainly not for a hobby project! Slightly better news, I found concrete evidence of this particular micro model in use for other UEI remotes (specifically JP1.3). This is clearly the driver for the infra-red side of the remote, which works fine, so I don't need to mess with it. And maybe I can find some community reference, even if just source code, for how JP1.3 works, and maybe it's just the flashing protocol for this micro?


The main attraction was saved for last. Given the lack of markings I have to make up my own numbering scheme. So, with the remote oriented as pictured, see that it is two columns of four pads. Pin one is the top left, and they go counter clockwise from there. With that set, I can show the map to ARM pins:


Jackpot! This is clearly the JTAG debugging header for the ARM micro! This is without a doubt the next area for me to concentrate on. I know what JTAG is, but so far very little about how it works. I've got an ST-LINK device, used for STM32 (ARM Cortext) work in the past which might be enough to move forward with. And if so that should give me full access to the ARM and whatever it has stored inside, plus I think I should be able to bit-bang SPI to the external flash chip as well, at least. I've mapped its pins to the SSP0 port on the ARM, no surprise, so it's accessible that way.

Fun aside: this had me very confused at first. For the lamest of reasons: I carefully counted out the pins and double-checked them all, thanks to the narrow pitch. I knew which went where for sure, looked them up and they made no sense. Only after a few back-and-forth attempts did I finally take notice of the "pin 1" marker on the chip. It's rotated 90 degrees counter-clockwise from the "natural" orientation. Compensate for that and the JTAG pins all jumped out.

Nevo C2 Remote Control - Reverse Engineering - Part 1

2016-03-07 19:36 - Making

I've been a fan of JP1 Remotes for quite some time. There's a wonderful community that has written software to put the user in total control of all the features they make possible, and even written "extender" software to add additional features. My approach for some time has meant turning on all the right devices (player, TV, receiver) and set them all to the right inputs, at the press of one button. Then turn them all off with the press of another.

Most recently I've switched to the "Nevo C2" remotes (also known as "Xsight Color" or "ARRX15G"), which have a graphical display built in. This makes it easy for me to deal with the huge array (TiVo, HTPC, plus eleven game consoles) of devices I've got hooked up. The built in software is pretty good, especially with RemoteMaster to customize it. But it's pretty clunky in some areas. At one point I found a post with pictures of the inside of my remote. The post was meant to highlight the (very minor) differences between two similar models. In the full size image, one can just make out a big ARM chip in the middle. I got interested in discovering more about the innards of these things, and how hackable they could be with some reverse engineering. So I ordered an extra one to take apart and tinker with, with no worry of damage. (They can be found on eBay for around $16, so this isn't a huge investment.)

The front of the remote. The back of the remote. The battery compartment.

Just for posterity, here's the external view of the remote. Front, back, and battery compartment. Forgive the crappy shots, this isn't the interesting bit. Except the battery compartment, which shows eight exposed pads which are fully accessible, at the bottom of a rather deep/narrow opening. What exactly they're for is very much worth looking into. But what I really want to do is highlight the insides. It's a good thing I bought a sacrificial unit to do this with. I cracked about half of the clips off to get the thing open. Brittle plastic, plus I didn't know the layout. I also ended up ripping the leads right off of the piezo buzzer once the two halves finally separated.

The PCB inside the Nevo C2 remote, full view. The PCB inside the Nevo C2 remote, close up of the interesting area with lots of chips.

First, here's a full shot of the immediately accessible (once opened) side of the PCB. The battery compartment is towards the left. On the far left are the previously mentioned exposed pads, plus a little circuitry which at first glance seems to be only related to the photodiode located there for learning capabilities.

The interesting bits are all at the other side, the right in this image. That area has been separately shot in a more close up view. I'm going to concentrate today on identifying the chips, so here's another copy of that image, with numbers overlaid for reference in the following commentary.

Close up of the Nevo C2 PCB, with chips numbered.

I've called out seven chips that seem especially interesting.

Chip 1

There's a large ARM logo at the top (with an "H" next to it), and STMicroelectronics logo at the bottom. The rest of the text reads:

KOR HP 948

This has got to be a STR911FAW42 chip which confirms that it's a 32 bit ARM MCU. The datasheet tells us that the 911FAW42 has 256+32 kB of flash and 92 kB of RAM, and comes in a LQFP128, which all seems right. Finding the programming pins, and ideally some spots that are more accessible than the tight pitch pints themselves, will be interesting.

Chip 2

This chip has no obvious (to me) markings besides the NXP logo which is upside down in this image. The text on it is:

L8C5M7      03

This turns out to be a simple 74 series 74LVC(H)16373A: 16-bit D-type transparent latch with 5 V tolerant inputs/outputs; 3-state. A latch/flip flop. Curious.

Chip 3

This tiny chip is unreadable in the images so the text transcription will be extra important. By the look of it, an eight pin SOP, I'm guessing serial flash.


First, I see the second apparent date code: this 37th, chip 2 38th, week of 2009. As far as I know these remotes are discontinued, so it looks like I've gotten some "new old stock" here, which might help explain how cheap they are. Either way, this definitely looks like the 32Mb, 2.5V or 2.7V Atmel DataFlash (Update: I had the wrong link, for part B not D here originally; Atmel doesn't have the D part on their site?!) by the part number on the second line. The remote supports adding custom icons, so the bulk storage in addition to the flash built into the MCU makes sense. This is the second part I'll be very interested to try to dump. It's probably wired straight to the MCU, but it's a much wider pitch part; I can solder breakout wires by hand without much fuss.

Chip 4

This chip is also small, and upside down in the image. A TI logo is visible. Its text is:


This turns out to be a SN74ALVC08 QUADRUPLE 2-INPUT POSITIVE-AND GATE, and the data sheet tells us that the top marking is indeed "VA08". The package lines up as well, so I have no reason to doubt this yet. The amount of glue logic is a bit surprising, though.

Chip 5

I've used an ISSI memory chip myself before, so I think I know what I'll find just by seeing the logo. But for completeness:

BE9622P1 0937

Yet another date code confirmation, this device is from late 2009 for sure. As suspected, this is a 64K x 16 HIGH-SPEED CMOS STATIC RAM, 1 megabit of RAM addressable as 16 bit words. I can probably ignore this chip. If I can dump and restore the firmware, I probably won't need to examine the expansion RAM. The bulk flash made sense, but I'm especially surprised to find a separate RAM chip on the board. I wonder what in the design necessitated this, that the RAM built into the MCU was insufficient?

Chip 6

I can see from a mile away that this is another standard series glue logic chip. The TI logo is visible in the corner, and the text:


We only need the second line to see this is a SN74LVC04A Hex Inverter. Nothing to say about that until I trace out where the connections are going. Physically it's between Chip 6 (RAM) and ...

Chip 7

This one's interesting! With my naked eye I can really only make out the bold Samsung mark. I need good lighting and magnification to make out the text:


This is as best as I can tell a S3F80KB 8-BIT CMOS MICROCONTROLLER, a secondary MCU‽ The plot thickens. Traces definitely must be found. What does this connect to, vs. the ARM MCU? Thankfully not terribly fine pitch, so again something I can work with. This is located towards the top, near the screen, is it related to that? There's also an obvious 8MHz resonator right next to it. Now I know why; I was surprised to see it before, when I saw what clearly seemed to be an SMD 24MHz crystal next to the main ARM MCU.

Interesting Bits

Near chip 7 are J8 and J6, two unpopulated 2x3 0.1" connectors. Near chip 1 is a metal tube, this is a tilt ball switch; the remote will (optionally) light up its display when moved.

Next Steps

I've got lots of things to do. An extra reason I wanted to order an extra remote to hack on is the firmware. All the ones I actively use are already in use, and I had to upgrade the firmware to be able to use them. I'm hoping to dump any contents of any flash memory on the device before ever plugging it in for real. There's a (mini) USB connector on the device (J1, near the bottom left of the close up view) for hooking up to a computer. I'd like to be able to compare the pre/post upgrade contents of the raw flash, plus make sure to monitor and log every possible (network, USB) interaction when upgrading the device. If I manage to do anything useful, it will almost definitely mean putting an alternate firmware together.

Figuring out where J6 and J8 go may prove enlightening/useful. Also the unlabeled exposed pads down by the batteries. There can't be much under the battery sticker, but some silkscreen markings are half covered at the edges, so perhaps something. Examining the other side of the board may be important as well, but these are tasks for another day!

Braun Electric Razor Repair

2016-03-05 11:13 - Making

Just under twelve years ago, I bought a Braun 7505 electric razor. I like this thing. I've needed to replace the blades several times, of course, but overall it's worked very well over time without any issue. Except the batteries. One of my favorite features was the batteries, meaning it need be plugged in only to charge, not to use. But the batteries didn't last. I finally decided to see if I could do something about it.

At first I found only one relevant page online: How to change the batteries in a Braun 7505 Synchro Shaver. It complained of a bad similar explanation on eHow (which I've not read), which referenced a manual without any instructions. So I found the Braun SyncroPro Manual and indeed, it has no instructions to describe replacing the batteries. But the Korean Syncro Manual does have these instructions, on page seven.

I've reproduced that image on the right. It's got unrelated English text on the page, but it's a nice visual description of the necessary steps. I found that prying the outermost cap (step 2) works best by grabbing the inner edge of the opening for the plug. I couldn't (confidently) get something around the edge like pictured without damaging it. Once that cap is off, the sides come off easily by hand, and some T9 torx screws hold the back on. With that removed the power board comes right out, it's held in place only by the structure just disassembled.

The original batteries have tabs welded on, which are soldered into the circuit board. (Maybe Korean models aren't welded in, thus the instructions in their manual?) I popped the tabs off by prying with a knife, which damaged them only slightly. With some replacement (NiMH) batteries in hand, I cleaned their terminals and heavily tinned them with solder, then set them next to the tinned tabs, then heated the whole lot until the solder melted together again. The original batteries were also stuck down with adhesive; some hot glue took that place with my replacements.

After reassembly, I've finally got a cordless electric razor again! I delayed this repair so long, it will actually be hard to get used to.