This chip makes building hi-speed USB 2.0 peripheral really easy. I like it!

Logic analyzer capture showing read and write transfer rate.

I did this project for teaching my learning remote the discrete on/off power code of my TV. The code sent by the original TV remote is the power toggle command. This is not so good when used as part of a macro for controlling multiple devices.

The remote that I have is the Sony RM-VLZ620. This remote is good and is cheap too. It can control up to 8 AV devices. Volume control button can be configured to control the AV receiver while the remote itself is in TV or DVD mode. 12 buttons can be configured to send macros. It is a learning remote, so any button can be made to “learn” from any other remote.

This project uses the Arduino hardware. All you need to buy to replicate this project is an Arduino board (about $30) and an infrared LED (about $2).

Even though I use the Arduino hardware, I didn’t use the Arduino development software, the code is written in good old plain C. You need to download AVR Studio (4.18 SP3) and AVR Toolchain from Atmel’s site, both are free.

Here is a sample Pronto Hex code and its corresponding generated LED waveform:
[sourcecode language="c"]
uint16_t ProntoCodeTest[] = {
0×00, // 0 – recorded waveform
0x6D, // 38kKhz. 0×67=>40kHz, 0x6D=>38kHz
0×01, // Sequence 1 on/off pair length
0×03, // Sequence 2 on/off pair length
0×05, 0×01, // Sequence 1, pair 1
0×02, 0×05, // Sequence 2, pair 1
0×04, 0×03, // Sequence 2, pair 2
0×06, 0×07 // Sequence 2, pair 3
};
[/sourcecode]

Here is the source code at Github

Infrared Remote Control Player by Stephen Ong is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License.

Hint: For debugging, you can use a digital camera (or phone camera) to “see” the infrared LED. Try it, it is pretty cool. Alternatively you can debug with a visible LED.

Sparkfun free day is part of Sparkfun’s marketing stunt that started last year where they gave away $100,000 with a limit of $100 per person. This year they increased the amount to $150,000.

I’m not sure $30 is worth the trouble of staying up from 3am to 5am pressing the refresh button on my browser. Anyway I’m happy getting the voucher.

I would’ve been extremely happy getting it. I was only in year 11 back then. I don’t know how I convinced my dad to pay $799 for it, must have been a lot of money back then.

I bought the oscilloscope from David Reid Electronics, one of the three electronics shop that was on York St, Sydney. I like that shop, it’s sad to see that shop closed down.

A Bit of Background
The two things I’ll consider in this review are safety and measurement confidence. Other aspects of the meter such as features and accuracy can be easily compared by reading the meter’s specification. Safety refers to how safely the meter fails. This can be due to an overvoltage or due to putting the meter in the wrong mode (eg measuring Voltage in the Current range). Measurement confidence refers to how much you can trust the meter reading.

Safety
The safety standard that applies to multimeter is the IEC 1010. When you see CAT rating of a multimeter, that CAT rating refers to IEC1010 Installation Category. That Installation Category defines the environment where the meter can be safely used. Most hobbyist would require meter with a CAT I or CAT II rating. CAT I would be for things like electronics circuit powered by battery or plug pack. CAT II would be things like appliances connected to wall outlet. For more information about the standard, see this overview by NI.

The sad fact is that many (cheap) meters lies about their IEC1010 compliance. Internal inspection of those meter clearly shows that those meters have not been build with safety in mind. A safe meter would have correctly specified protection devices such as fuses (ceramic instead of glass fuse are often used for the high interrupt rating capacity), MOVs (the more of them, the bigger the better), PTC, and appropriately sized air clearance and creepage distance. Unsafe meter is dangerous. See this video for demonstration of unsafe meter.

Safety in Fluke 17B
The Fluke 17B claims CAT II 600V rating. (Manual claims CAT III 300V, but only have CAT II 600V printed on the body). However the supplied probe is only CAT I rated (Not the standard Fluke TL75 probe) . The 17B cannot be used in CAT II areas without replacing the probe.

Is the 17B compliance real? Unlike other Fluke models, the 17B does not have Underwriters Laboratory recognition. The manual claims that the 17B is certified by CMC. I don’t know who CMC is. Internal inspection of meter suggests that the 17B has been designed to comply with the standard. See part I of my review for internal photos.

Measurement Confidence
Measurement confidence is an important aspect of the meter. It is very important to be able to trust the meter’s reading. To most people the brand Fluke is synonymous with reliable measurement. Measurement confidence depends on many things, both objective and subjective. For a start the meter must meet it’s accuracy spec under reasonable operating condition. The meter must be robust, a reasonable knock must not throw off its calibration. The meter must not have strange anomalies, etc. Here is a list of things that affect the 17B’s measurement confidence:

The good:
Build quality is an important aspect of measurement confidence. The 17B build quality is very good. Body is solid. Probes are good. Probe socket makes good solid contact. Function dial is good.

Display is good. This may seem trivial, but clear display helps avoid measurement error. The 17B LCD is big and clear. Decimal digit is displayed clearly. Measurement mode and unit are clearly displayed on all setting.

I performed accuracy spot check on my meter. All measurements (except for low value capacitance) are well within the accuracy specification.

The bad:
Displays incorrect value just after auto-ranging. The reading overshoot for one sample reading.

Measurement are generally fast, however resistance autorange is slow. It takes about three and a half second to measure 100Ohm resistor.

Continuity tester is annoying. The meter goes beep, then random duration of silent for a fraction of a second, followed by continous beep.

The meter struggles with low capacitance measurement. Without any capacitor connected, the meter displays a residual 0.53nF. The residual capacitance can be nulled out by pressing the “REL” button. Even after nulling out the meter, it still has trouble measuring capacitance <10nF within its accuaracy specification.

With temperature reading, the meter reading jumps when the meter is rubbed. I have no idea what causes this, static or something.

Conclusion:
The Fluke 17B is a good basic meter. It’s not good as other Fluke meters but is still a good meter. It is much better than no-name brand meters.

I am happy with proto-advantage service. Out of the other online stores, they offer the cheapest ($5) delivery to Australia. They processed my order quickly. Within half an hour of ordering, I received my shipping confirmation!

First impression of the Netduino is very good. The team that designed the board paid attention to details.

The “small box” packaging is nice:

I like the custom font on the trademark name “netduino”. The are consistent with the use of the font; they are used on the PCB, packaging and website.

I like the consistent blue colour scheme. I like how the header connectors are blue. Much nicer than the traditional black. I like how the user LED is blue. They made additional effort to use the blue LED rather than the standard red or green LED.

The power indicator LED is white! It’s different. I like it. First time I see diffused white surface mount LED.

I like how they choose Micro-USB connector. The Micro USB can withstand much more insertion cycles compared to the Mini or the full sized connector. I like how they choose the USB connector with through hole reinforcement.

I like how they have ESD and resettable overcurrent protection on the USB line.

I like how they provide rubber feet.

I like how they supply you with Micro-USB cable. (As I understand it, it is only promotional)

Here is the Netduino compared to the Arduino. As you can see netduino keeps all the mechanical aspects of Arduino.

Overall, there are many things to like about the netduino. Now, lets start coding for it…

The idea itself is not new. GHI Electronics have a product called FEZ domino which is quite similar. What sets Netduino apart is the open-source firmware and the cheaper, $35 price tag.

I’m placing an order for one. I’ll post my review after I receive the board.

Update (21 Oct 2010):
I’ve received the board and have posted my initial impression.

This Fluke model is only for sale in China, however you can easily get this model from Ebay or DealExtreme. Given that it is only for sale in China, there aren’t many in depth review of it. My concern is that this model may not be of the same quality as the other Fluke’s model.

This meter has a sister model, the Fluke 15B which does not measure frequency nor temperature.

For more information, calibration manual of the meter is avaliable from Fluke China website here.

First impression is good, the meter looks and feels like a Fluke meter. The meter feels sturdy. The LCD is big and clear. The function selector dial is good, it gives that positive “click” feeling.

Compared to the Fluke 77, this meter has better functionality in that it measures current down to the µA range, measures capacitance, and measures temperature using the provided K-type thermocouple probe.

The downside of the meter is that it doesn’t have Fluke’s auto touch hold, no-bar graph, and no LCD backlight. The overvoltage CAT rating is also slightly lower (300V CAT III vs 600V CAT III).

Compared to higher end Fluke models, this meter lacks the min/max function, does not measure true RMS and has no incorrect probe socket detection.

Internal contruction of the meter is really good. You can see the well designed PCB, the high quality components and the good soldering from the photos below. You can also see the big HRC fuses and the MOVs used for input protection.

Here is a link to the high resolution photo.

I have yet to evaluate the performance of the meter I will post my findings in a later blog entry.
Update (9 SEP 2010): Continue to the second part of my review.

I had difficulty justifying the purchase of this oscilloscope, as I had doubts on its usefulness and performance. However, the unit has such cool form factor that I just had to have it. The oscilloscope is modestly priced at USD $89. I justified buying it because, if for some reason the oscilloscope is not usable, then I still can use it as an ARM STM32 development board (Hey, this is the same CPU that powers Hexi’s locomotion engine).

First impression
The unit is very small and light. The build quality is reasonable but feels rather “plasticy”.

The alignment of the LCD to the display window is slightly off, a few left-most pixels are not visible when viewed straight on.

Push buttons are good, they have nice tactile feel. The slide on/off switch is not so good, the switch is difficult to slide and the swith doesn’t provide that “clicking” feedback.

The supplied probe (or rather test clips) is quite usable. Probe cable length is 0.5m. This is a good length, given that the unit can be easily placed close to the project you are debugging.

A nice soft pouch is provided for storing the scope.

Display
The display is a 2.8” 320×240 LCD display. The display is very good. The screen is crisp, bright, and of high contrast.

Obvious Limitations
There are obvious limitations to this scope. You should be aware of these before buying the scope:

• Firstly, it is a single channel scope. This means that you have no chance of seeing timing relationship between two signals.
• Secondly, the sampling rate is limited to 1Ms/s. This limits the usefullness of the scope to signals lower than 100kHz. This is very low for an oscilloscope. This is sufficient for audio signals or slow speed digital data like 115200bps asynchronous serial.
• Thirdly, the input stage is only DC coupled. Without AC coupling you can’t see small ripple superimposed on large DC voltage.

Performance
The refresh rate of this scope is good. The responsiveness of the user interface is also good.

On some vertical gain settings (2, 5 and 10V/Div), the vertical accuracy is off by 8%, while on other settings the accuracy is off by 2.5%. There are no means provided, either by firmware or by trimpots to adjust these vertical gains. On my scope I trimmed the gains by soldering extra resistors in series/parallel with the gain setting resistors.

Input stage capacitances have not been tuned to provide flat frequency response. On the 2, 5 and 10V/Div settings, with square wave as input, there is a large 16% overshoot. On my unit I manually trimmed these by soldering extra capacitors on the provided unmounted pads.

There are AUTO, NORM(al), SIGN(single?), NONE, and SCAN triggering mode. AUTO works as expected. NONE starts capture without waiting for any trigger condition. SCAN also start the acqusition without waiting for trigger condition. The difference is that SCAN don’t fill the entire capture buffer, the screen refreshes as soon as the trace hits the right of the screen. I can’t get NORM and SIGN to work.

There is positive and negative edge triggering option.

There are two horizontal and two vertical cursors provided. Time and voltage differences are displayed on the status bar. The cursor’s line can be turned on/off.

Timebase accuracy is spot on as expected.

Things I don’t like about the hardware
Battery wires are soldered directly to a couple of surface mount pads with no mechanical strain relief. This is bad. Overtime this solder joint will break, possibly shorting the battery.

The unit do not have any kind of EMC shielding. The PCB itself is only a two layers board with no ground plane. This oscilloscope is definitely not intended as a professional equipment. In the presence of strong electromagnetic radiation, you will get erroneous reading.

Noise is visible on high sensitivity setting.

The input amplifier exhibits high gain at high frequency for gain setting of 2, 5 and 10V/Div. With square wave input, this shows itself as random spikes at the square wave transitions.

No anti-aliasing filter in the hardware circuit. This is especially necessary because of the low sampling frequency. Any frequency component of the signal above 500kHz will be aliased in and will confuse the reading.

Horrible battery charging circuit. The lithium polymer charger consist of a 1 Ohm resistor in series with a diode connected to the +5V USB. This is NOT how you charge a lithium battery. There is provision on the PCB fo a proper lithium polymer charger chip to be mounted but Seeed Studio in their wisdom decided that a diode circuit is sufficient. This diode circuit must be replaced with proper lithium-polymer charger chip. I am currently trying to ask Seeed Studio to send me this charger chip.

Things I did not like about the firmware
User interface is difficult to use.

Scrolling through the 4096 points capture buffer is painfully slow.

There is no trigger hold-off setting.

NORMal and SINGle triggering options do not work.

Things that I did not test
The oscilloscope has a 10x setting for use with a 10x probe. I do not see the advantage of using a 10x probe with this oscilloscope.

Captured trace can be saved to an optional micro SD card. This trace can also be transferred and displayed on a PC. This feature is nice but is not very useful for me.

It has automatic measurement feature. It measures DC.V, Vavg, Vrms, Vpp, Duty, Cycle, and Freq. This is nice, but I’d rather use the built-in cursors to make measurements.

Things I like
Did I mention the small size?

Did I mention the beautiful LCD screen?

Battery powered means the oscilloscope is floating so I can connect the ground probe to any part of the circuit.

The firmware source code is available for modification. Currently, only source code for older firmware is available, but I am hoping that they would release the source code of an up-to-date firmware. Additional features like data logging can hopefully be added.

Conclusion
This oscilloscope is cool and fun to use, however there are hardware and firmware problems that seriously degrade the quality of the product. Many of those problems should be easily fixable.

The scope does have its limitations. This scope will not be suitable for everyone, it is not a “real” scope replacement. However if you are aware of its limitation, then this scope is very capable and great addition to the toolbox.

Alternatives:
I know that the products I list below is not in the same price range as this oscilloscope, however I find them to be very good, so you may want to consider them:

Consider getting a second hand Tektronix 2400 series oscilloscope. The Tek 2400 scope is really good.

If a logic analyzer would suit you better, consider the Intronix LogicPort logic analyzer.

If you really want a digital storage scope, then those Rigol scopes are good value for money.

If you do have lots of money and I mean lots, you can consider getting the Tektronix TDS5000 series oscilloscope. I’ve used a TDS5104 at work. It is really good and it is the first digital scope that I used where I didn’t feel I’d rather use an analog one.

Meet Hexi. Hexi is my new 6-legged robot (hexapod) family member. He is demonstrating the three standard walking pattern for a hexapod: wave, tripod and ripple gait. For now he can only walk in a straight line.

Body: Lynxmotion Phoenix
Actuator: Hitec HS-645MG servos
Processor: ARM Cortex-M3
Battery: 5 Sub-C 5000 mAh (cheapbatterypacks.com)