I’ve been playing with Polar heart rate (HR) receiver for a while and it is really easy to use. So, I decided to open up the recumbent bike’s console and replace the hand-grip HRM system with the Polar HRM system.

Let’s start with the Polar RMCM01 HR receiver unit. All you need is 3 additional components to make it work; couple of 1Kohm resistors and a 32.768 kHz, 12.5pF load capacitance crystal. Follow page 7 on the datasheet to get together your Polar HRM device or see below.

Here is the Datasheet. (I can no longer find any stand-alone RMCM01 units for purchase. SparkFun stopped selling stand-alone units for some reason, they only have it mounted on an interface board.)

Once you build your sensor, you can hook it up to 3V DC, put your chest strap on and test it with an oscilloscope. The unit sends 1ms pulse of 3V every time it detects a heart rate. Here is an example output form the unit when it receives the HR.

As you can see, the frequency of the signal is 1.359 Hz. You can calculate the HR with a simple calculation: 1.359 * 60 = 81.54. So the HR is about 81 beats per minute (BPM).

How to hack the bike’s computer:

Unfortunately I forgot to take a picture of the board before I removed the hand-grip HRM unit and made modifications, so I’ll try to illustrate the original condition on the modified board.

The black block in the picture is where I found the original hand-grip HRM unit. It looks like this:

As you can see it is pretty much a black-box. If I wanted to fix it, I had to remove all that epoxy or resin they used to protect the unit, too laborious for me to tackle. It, however, gave clues as to how it was working. When you look at the board you see ports marked L and R, this is simply for the hand-grips and there is nothing interesting there. What I have left with V+, G, P0 and P1. V+ and G are obvious. So the business end of this unit is P0 and P1. Since the unit was not working, I had no idea what type of signal it generated. When I tested the console without the HRM unit installed it did not show the little heart symbol on the screen indicating that it wasn’t receiving a HR. When I installed the HRM unit back on, the little heart symbol was erratically blinking, indicating that the HR was present but couldn’t calculate what it was.

So, I hooked up my oscilloscope to the P0 and P1 lines to see what was going on. The P0 and P1 was low when the unit was off. When I turned the unit on, both P0 and P1 was going high and staying high. I un-hooked the P1 to see what the little heart console indicator showed. Surprisingly it showed HR detected. When I un-hooked the P0 and hooked P1 back on, the indicator showed no HR detected. So HR detection is controlled by P0. When P0 is high HR is present, when it is low HR is not present. Great!

I needed to figure out how P1 was sending the heart signal. At this point I assumed the fact that the P1 line is sending some kind of a square wave indicating the HR. I grabbed my signal generator, set it up to the same amplitude the circuit was running on (4V) and generated 1 Hz square-wave signal. I started the console, pulled P0 to high and fed 1 HZ square-wave signal to the P1. Several seconds later the console on the bike displayed a heart rate: 60 BPM. Bingo!

Square-wave I generated was symmetrical, but the Polar unit generates 1ms pulse, can the microcontroller on the bike’s console read the 1ms pulse signals? I just had to try and see. I hooked the Polar HRM unit’s HR output the bike’s P1 input. Several seconds later, my heart rate was shown on the console. *grin* That was easy.

Now, I had to make my modifications on the console board and find a 3V power source for the Polar HRM unit. Here is what I did:

I found couple of BA033ST 3.3V voltage regulators on the console’s board. I decided to hook the Polar HRM unit to one of them. However the output of these voltage regulators were hovering around 3.4V, which is the maximum voltage Polar unit can accept. To be on the safe side I wanted to use a voltage below 3.4V, so I decided to add a 1N4001 diode to the voltage regulator’s output to drop the voltage. Since the 1N4001 have a forward voltage drop of 0.7V, it pulled the voltage down to a safer range for the Polar HRM unit. See below:

This is before I modified the board.

After the modification.

Now I had to permanently pull P0 to high. This was relatively easy as all I had to do is to add 10 KOhm resistor to the V+ (4V) coming out of the board and connect it to P0 (Marked PE on the console board). It would’ve been better if I used FPLS output from the Polar receiver, but I neglected to hook a wire for that output so I used this method instead.

Before the modification.

After the modification.

Now the hookup is complete, I had to find a nice cozy place for the Polar HRM unit. Luckily right bottom of the console there was a perfect place for it.

All done. Here is a video that shows how the unit functions now:

Thanks to my wife, I now have an additional desk for electronics projects:

Now the lab is in order, I decided to start up with a repair work. I picked my broken Logitech Harmony 670 remote for this job. It is more than 2 years old and was in perfect working condition as far as the remote functionality goes. The problem arose when I try to update it with a new activity by connecting it to my computer. It just wasn’t syncing with my computer even though my computer detected it. Logitech wasn’t helpful as it was out of warranty. So I opened it up on the new lab setup. To open the remote, first remove 4 screws shown in the picture.

Use an iPod/iPhone Pry Tool (shown on the left) to pry open the case (shown on the right)

There are total of 6 plastic tabs that hold the case together as shown below:

I narrowed the problem down to the USBN9604-28M USB controller IC. It operates on a 24MHz clock but the oscillator circuit wasn’t generating the signal required. Since I didn’t have a way to test the crystal in a quick fashion I decided to replace it. That did not solve the problem. I realized that the C5 (15pF) cap was bad too (or that was the culprit to begin with). I replaced the cap as well. See below.

The unit worked briefly until I knocked it over my desk. Upon inspection I realized that Logitech did not solder the USB connector casing to the board at all. So I messed up the USB connection by knocking it over my desk as the USB connector got bent. After properly soldering all the connections and the casing to the board everything worked like a charm.

I spent about couple of hours working on the remote. I could’ve gotten a refurbished one for about $70 and a brand new one for about $120. But, this is not about the money. I got a great satisfaction by fixing it, and also prevented another electronics item to go to a landfill.

Your first option is your router, does it have logging capability? Is it turned on? If your response is yes to both of these questions, you can try to locate the MAC address in your router’s log. I wasn’t that lucky as my router does not log the MAC addresses of the traffic unless it is an attack.

Do you have another Windows system that you can access to? If you have another system and if you have interacted with the target system using this other system you might get lucky. Search the registry of this system to find out if there are any clues. Search target system’s computer name or ip address. I got lucky with that method by searching my target system’s computer name in the registry. Windows Media Player’s Play To functionality keeps a record in the registry for the systems it previously interacted. On Windows 7, it is located at HKLM\Software\Microsoft\Windows Media Player NSS\3.0\Devices, and it stores MAC address, ip address and computer name along with some other information. Device names under this key are MAC addresses of those systems/devices.

That’s how I found my MAC address, and using my Ubuntu system in the same network I was able to turn the target system on. Ubuntu (or another LINUX system) have a tool called wakeonlan, or alternatively you can use etherwake. The syntax is pretty easy:

“wakeonlan <Target MAC Address>”

You can get more information about Wake on LAN at Wikipedia.

During the conversion, I decided to abandon my highly customized theme. It was based on an old theme that didn’t accept widgets, which made it cumbersome to make changes. I did make certain changes in the new theme as well, but it is minimal.

Transferring data from the old blog to the new one was pretty easy by using the export/import functionality. However, I am noticing that some of the characters did not transfer properly such as single quote. Also export/import process does not bring plugins or configuration settings. Thankfully I don’t run many plugins so it went rather smoothly.

I like to fresh new look of the site and the bigger fonts. Who knows this might even increase the frequency of my blogs.

“Computer problem” so called Captain has said.

“You know like any other computer, we think rebooting it will fix it. But, FAA regulations don’t allow us to do the reboot while you guys are on the plane so we need to let you guys out, so we can safely reboot”. This plane must have been using Microsoft Windows operating system.

“So leave your stuff in the plane and exit, we’ll be on our way shortly” he finished.

Leave my stuff on a broken plane? No way, I grabbed my backpack and walk out of the plane. We started waiting at the gate for plane to reboot. After 45 minutes of waiting, Mr. Captain showed up at the gate.

“Well, we rebooted the system but the computer is not coming online. We either have to switch the plane or switch this very expensive board. Unfortunately our parts depot is at Oakland.”

He took his hat off and put it under his arm and continued:

“I am an honest man, and I cannot jeopardize your safety. Unfortunately it is not 1930’s that all you need is a plane and an engine. We cannot fly the plane without the computer board.”

It sure isn’t the 1930’s, so I expected a bit better of a customer service, such as testing the plane before pulling it to the gate, and rectifying the situation before it became a problem at the very last minute. Considering the next plane was at 8:40am, it was impossible for me to get to my appointment in time. So, I had to wait in the customer service line along with other 100 or so customers and get a new flight for the next day. By the time I got out of the airport it was rush hour time and took me over an hour to drive back to house.

Lets hope I’d have better luck tomorrow.

That said, I own two iPhone 3GS phones, I don’t have a case, I only am running the iOS4 on one of the phones. I cannot say that holding the phone was a problem for me, but again I don’t use the phone w/o a headset because I don’t like to expose my head to a lot of RF emitted by these devices. So your best bet is not the bumper/case, your best bet is the hands-free headset. Just keep the darned phone away from your head and try not to hold it in your hand while you are talking on the phone.

Since I am ranting about Apple stuff, let me give you an update on the iPad front. If you remember, I mentioned the wireless problems I was having with my iPad in my previous posts. We were vacationing at Napa County and Mendocino last week, so I took my iPad with me. iPad behaved perfectly in two different wireless networks during my vacation. So, I decided to use another wireless router for my iPad and set up a WRT54g, one of the new sleek looking ones. I didn’t see any problem with wireless since. Perhaps Apple tests the iPad with common routers such as WRT54g and didn’t test it with newer, less common routers. Is there a pattern emerging about the Apple’s quality control here? Time will tell…

What is a GeoGiftBox™? It is a locked Antique Wooden box fitted with electronics to detect its current location that opens only if you are standing near the location it’s programmed to open. I will give more information about the box, and how it’s been used in my engagement process, and where can you purchase your own box later.

iPad:
I love the iPad, however, which it is a big one; my iPad loses its wireless connection sometimes to a point that I cannot make it rejoin back to my network. You might think that it is my router that has a problem, or my home network configurations, but hear me out first. Between me and my girlfriend we own 5 Apple products. I have 2 iPhone 3GS and an iPad, my girlfriend has an iPhone and an iBook. When my iPad is having connection issues with my CISCO (wel,l a router can’t get any more industry standard than this) router, all other 4 apple devices that we have works flawlessly along with my personal windows Laptop and my work laptop. So the *only* system having problem with wireless is iPad! I am not alone with this problem either, according to Apple techs I spoke with during the last 3-4 months, many others are having similar issues.

Strangely though, when I grab my iPad when it is not working with my home wireless and other wireless networks, and take it to an Apple store, it magically starts working again in their wireless network! WTF!

If there are 6 systems working with my home wireless network flawlessly when iPad is having problems with my wireless, the problem *cannot be* my wireless network. What did Apple do to fix this problem? diddly-squat. Supposedly the upcoming 4.0 OS will fix the wireless problem, but the same OS was loaded on Steve Job’s iPhone 4 when he was introducing it to the public and he even had issues with it. Is it lack of testing? Is it the new wireless chip/drivers they are using? Do I care? NO. The only reason I buy Apple products over Windows/PC products is because they just simply work without problems. I cannot say the same thing for iPad though. It still boils my blood when the wireless stops working for no intelligible reason at all.

WinZip:
Well, I don’t use WinZip to begin with. I use WinRar, because I mostly work with RAR files than zip files. WinRar can also open ZIP files along with many other compression formats. Now I just learned that there is a new file format created by WinZip called zipx. Of course, the only way to unzip this new file format is to use WinZip. Even though it is a clever move by WinZip, it is very annoying for those who doesn’t own or use WinZip. The dilemma here is a bit complex though. WinZip managed to find a way to compress media files such as JPG files much better with this format. For example I compressed 13 JPG files totaling 81 MB with RAR and ended up with 81 MB RAR file, same thing was the case for ZIP, but the ZIPX archive was 67 MB. Pretty nifty eh? Would I buy WinZip just because that I can compress media files better? NO! Storage is cheap, I have terabytes of storage on my systems at home and unlimited storage in my Smugmug library, also I have unlimited cloud backup through Mozy. So, even though WinZip has better compression for media files now, it could be a bit too late, and it definitely is annoying as the best price for a compression application nowadays is FREE.

I look at iPad as an e-book reader type of device. It surely is way too big to carry around for listening music. You can get much better experience surfing the web with a regular netbook or laptop so it is not iPad’s strong point. I am not sure if it would be a good device to email with for long periods of time. Once you eliminate the things it cannot do well, you understand what is this device is for. It is a content consumption device. So you can read your newspaper, e-books and watch movies with it on the go. I think it is a brilliant device for content consumption. That is very important for me as I don’t like to be tied into a single publisher when it comes to e-books. Amazon, Sony, Barns and Noble and now Apple is out there delivering e-books. Sony’s e-book store is a joke as its prices are not competitive. They suck at delivering content. Amazon was to first to arrive in this market but they do not have as many books as B&N at the moment. I don’t know how Apple’s iBook store is going to be like. There is one major advantage iPad has over other e-book sellers: iPad has applications for Amazon Kindle and B&N Nook. So, you can select your content provider by book basis. How cool is that? If you get a Kindle you stuck with Amazon, if you get a Nook you stuck with B&N, but if you get an iPad you can use any one of these services. That practically is the selling point for me.

However, a PC can also do all the same. You can read iBook store books with iTunes, Amazon and B&N both have readers for the PC. So, if HP comes up with a better device built on PC platform that has more features and better price, it would be a very attractive option. Especially considering HP is not in the content delivery business.

It concerns me that Apple has complete control over the app store; they simply can shutdown Amazon and/or B&N by not allowing their applications on the app store. I most certainly don’t want to get stuck with iBook store, especially after paying significantly more amount of money to an iPad over Kindle or Nook.

That’s why I am in a holding pattern. I waited this long, I can wait another 2-3 months.

Barns & Noble's new e-book reader: Nook

I wrote an article about Kindle 2 before and mentioned the shortcomings of Kindle. To recap it really quickly, Kindle 2 did not support PDF files natively, did not have memory expansion and at the time I wrote the article it was retailing $350.
So how does Nook fair against Kindle 2? First of all Nook solved the problems I have with Kindle 2 by providing memory expansion and native PDF support. So they already met my requirements for a good e-book reader. All for $259, but there is more: They’ve added Wi-Fi support and 3G connectivity for free, also a color touch screen LCD screen at the bottom for navigation etc. I am not sure if I like this feature to be honest. Why would you put a color LCD on an e-book reader instead of expanding the reading screen? I think the designers of the Nook a bit carried along. I understand that they did not want to use a physical keyboard like Kindle 2 is using, but does it really have to be a color touch-screen? Because of the color touch-screen, the battery life of the Nook is significantly less than Kindle 2. I’d say if you are not going to be able to make the entire screen color and touch sensitive, do not make it touch sensitive at all. Also the device is not fast at all. Isn’t it time that someone comes up with an e-book reader that can turn pages faster than 1 second? I am sure it is part of the e-ink technology’s problem. Another issue with the Nook is the update times being different between the color LCD and the e-ink screen. This is making the navigation confusing; yet another reason not to use the color touch-screen.
So can the Nook take over the leadership Amazon has in this market? I think it can and I think it will. B&N has another advantage; they are claiming that they provide many more e-books than Amazon, about three times more in fact. If B&N can keep the competitive price point, I don’t see why they cannot win.
I don’t think Kindle 2 can compete with Nook if Amazon keeps selling it for $259, Kindle 2 just doesn’t have all the bells and whistles Nook has, B&N has more books to offer. That said, B&N has missed a major opportunity because they couldn’t time their launch of Nook.
Bottom line is this: I will get a Nook. If you are in the market to buy an e-book reader, get the Nook.