Wednesday, February 27, 2013

Convert your old SRM power meter to ANT+

So a while ago I noticed some posts in the ANT+ forum by Mark Rages. Turns out he’s the “electronics guru” of Quarq. He has an old tumblr site here. Where he shows an MSP430 + the ANT+ AP2 module to use as an intermediary and convert old SRM powermeters to ANT+.

This is like my ANT+ to BT2.0 for another purpose… a much more complicated issue too. If you have an old SRM this should be very useful to you!

Image from markrages.tumblr.com

This is impressive! He’s gotten power consumption down to 160 microamps from a coin cell. He’s a much more experienced man than I in regards to this stuff.

There was also a discussion on Facebook’s “Training with power” surrounding ANT+ head units. Mark’s post in the ANT+ forum was removed or I can’t find it, however the opensource.quarq.us site still exists with his python scripts for ANTware II. It’s located here.

A big shout out and thanks are deserved for Mark I think. Cheers and thanks for promoting ANT+.

16 comments:

  1. It's a cool-looking project. I downloaded his code to play around with it, but it won't compile for the chip he says he is using due to the size of the compiled code. I've got an email out to him to see if he's using a different toolchain than me, or has some sort of black magic incantation that needs to be whispered before running make.

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    1. I've tried to contact Mark a couple of times without success. He popped up with a lot of stuff around the time he made the post, and then very quickly disappeared from involvement with the ANT+ forum.

      That's too bad about the code not compiling. Maybe the chip he listed isn't the correct one?

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  2. Mark and I have corresponded briefly. He's been extremely helpful both on the software front as well as offering suggestions for working with the SMDs he specified in his layout.

    The object file, even with the most aggressive compiler optimization, is frustratingly 50 bytes too big to fit in the MPS430g2231 memory. Mark suggested using another msp430 with identical pinouts - I've been able to compile for the 2302, 2312 and several others and get the code to run in my emulator. I've got a 2312 on order for my launchpad as well as the other parts. If I can get things to work on a breadboard I'll order a few of the PCBs per Mark's design and see if I can get my 2 wired SRMs talking to a garmin.

    I don't know how embedded software guys can do this every day. I've never had to worry about 50B of text in one of my executables before :)

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    1. Hey John, im trying this project as well. Ive ordered the necessary parts and am going to attempt to recreate the project. Will you be posting your results anywhere? If you dont mind, i would love to keep track as it may help me complete my chip as well.

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  3. Luckily I've never been so limited, but this sounds frustrating... maybe even infuriating! I'm moving my design to the nRF51 as the transceiver is built in with the ARM core. It seems quite flush with memory so hopefully I don't start running into similar problems.

    If you have some success John, I'd love to hear about it. Keep in touch. It looks like such a useful project that if I could get an old wired SRM unit I'd consider building it so I'm hoping to hear you've been successful.

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  4. Being an owner of 4 older SRM's, these projects are of great personal interest to me. I bought a couple MSP430's, and some ANT+ modules. I'm waiting for the modules to arrive (Wednesday) to see if I can make it work. Looking through your most current project, I'd love to help in any way I can.

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    1. There seems to be a decent amount of interest in this. I've gotten several emails about it. If you get anywhere I'd love if you could email me and let me know. Several times talk of needing to use a different chip than Mark did has come up with people I've talked with -- lack of memory. There might be a drop in replacement. Anyway, keep us / me informed if you have a chance.

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    2. I don't pretend to be an engineer. I am decent at reverse engineering and copying. I'm primarily a cyclist and a very experienced coach. Parts came in today. Let's see what happens.

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  9. Great! If you ever hit the market, I have two older wired SRM and would surely get these convertion systems!

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  10. Hello Keith, How's your project going with the SRM convertion to wireless ? I've been looking for something like this for awhile. I was thinking about doing same thing use a Bluetooth chip. Would love to hear how are you doing on this. Thanks

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  11. Hi, I wonder if anyone who attempted the building would have any additional information to share here. Since there were no follow ups I tend to believe no one succeeded - is that the case ?

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