3 ms·

Reverse Engineering a VanMoof E-Shifter – Part 2 – Decoding the Signals

47 points by jandeboevrie 2y ago

mcntsh 2y ago
> The reliability of this e-shifter in the X3 and S3 has been argued as the cause of the failure and eventual bankruptcy of VanMoof I always wondered what exactly the problem e-shifters were trying to solve was. Is it the "ugliness" of shifting cables? Route them through the frame...
- morsch 2y ago
  I doubt it's about the cabling. It's convenient not to have to think about shifting, like an automatic transmission in a car. I sometimes wish my bike had it.
  - amluto 2y ago
    Good luck. With a derailleur, no amount of e-shifting magic can shift while stopped. And even with a hub shifter, most “automatic” systems I’ve used have an annoying failure in which you slow or stop briefly, try to start pedaling again, and discover that the system has chosen that moment to downshift several steps and you actually can’t go anywhere until it’s done.
    - morsch 2y ago
      Yeah, I'm not holding my breath.
- mtts 2y ago
  Regular shifter cables can and are also routed through the frame. Expensive road bikes (as well as the ones professionals ride) use e-shifters without any problems. These are made by companies that have some expertise in manufacturing shifters. They’re very expensive, though, as they’re made for road racing, not for regular bikes like the ones VanMoof made. VanMoof wanted to do everything themselves and found out the hard way that was a bad idea.
- ndsipa_pomu 2y ago
  I've got Shimano Di2 shifters on my road bike and they're very luxurious to use. Advantages: The controls are simply electronic switches, so you don't need much finger strength to operate them (reputedly these make them useful for people with hand strength issues such as arthritis) and also this means that you can reconfigure them (e.g. a one-armed cyclist can move the relevant controls to just one side) or even add extra controls such as sprinter buttons. If you've got double/triple chainrings, then the gear change can incorporate the switch-over point so you can just change up or down a gear and let the electronics handle when the chainring shift should occur (this can be changed in the software too according to your preferences). Also, with regards to the chainrings, the shifting system can adjust the front derailleur to accommodate the chainline better i.e. the front derailleur may need to be a mm or two further over for the smallest or biggest rear cog to prevent the chain rubbing. That's commonly referred to as "trim" and can usually be done manually on a manual gear system. Probably the biggest benefit is highly reliable shifting - once set up, it will perform perfect shifts every single time, whereas traditional gears will need adjusting as the gear cable inner stretches over time. As to disadvantages, the biggest issue is the price and the next problem would be that you need to keep the battery charged up or otherwise you're not going to be able to change gear. Typically, a single charge will last for thousands of shifts or a few months. I've also had the battery fail and unfortunately, they're very expensive to replace as the battery component also houses the main electronics for the system (e.g. the brain).
  - mcntsh 2y ago
    An indexed shifter can also perform perfect shifts for thousands of times, and after that time you don't need to change out a battery you just need to maybe turn the barrel adjuster a few mm. The chainring thing is cool but front-gearing is also sort-of on the way out in favor of 1x groupsets. One of the greatest things about bikes, IMO, is how elegantly simple they are and how that translates into reliability and ease of maintenance. The push to using electrical components feels like a step in the wrong direction in this regard.
    - analog31 2y ago
      Note that the VanMoof was an e-bike with a lot of built-in features, so it wasn't intended to attract a minimalist market in the first place. The point is, it's an everything bike, in a stylish package.
- analog31 2y ago
  Trek Lime had an automatic 3-speed, circa mid-2000's. A friend of mine had one. I don't think there were ever widespread reliability issues. Sram had a 2-speed automatic that was fully mechanical.
- tonyedgecombe 2y ago
  My wife struggles with shifting gears so an automatic shifter would make things easier for her.
cubeflake 2y ago
Nice write up! I am also fiddling with my bike and have just figured how to pull the binary from the main M4 soc. Perhaps you could share your work with https://github.com/Bernardus/openmoof https://github.com/Bernardus/openmoof (Not my repo but has a lot of good info, I plan to share the binary as well once I made some progress in reversing it)
vr46 2y ago
Intriguing stuff here from a geek perspective, as I have an X2 and am only plagued by a lack of gears. I would expect e-shifters to have been made reliable by the time the 3 series came out, I didn't realize they were that bad, especially as I would love to see them everywhere. Having to adjust my son's bike shows how tough shifting gears can be, and the cable is constantly stretching. Plus, the whole getup freezes in winter.
Neywiny 2y ago
Can the second analyzer software not do the same measurement as the first? Coming from a point of ignorance here: I lucked into some higher and DLAs (though not 5v compatible so they wouldn't directly help here) and their softwares allow both decode and measurements
- crote 2y ago
  Yes, but only in hindsight - and you have to take the "part 1" into account too. An oscilloscope is able to show analog values. If you have no clue what a signal is, it is your best bet to start with. In this case it turned out to be a simple digital serial signal, but it could've just as well been a 0V-5V analog one or perhaps an open drain bus with pullups like i2c. Logic analyzers only really work for binary values. You are able to set a single threshold: everything above becomes a 1, everything below becomes a 0. Great if you've got a purely digital signal, useless if it has analog components. In the first part the author had to start with an oscilloscope to begin exploring. They could've probably switched to the logic analyzer before the first step of part two, but there isn't really a strong reason to do so - and there would still be a nonzero chance of analog components playing a role. Seeing that it was a simple digital "one wire TX, one wire RX" probably gave enough confidence to assume it was something like serial uart and move on.
  - Neywiny 2y ago
    Maybe I wasn't clear enough, I meant cutting out the gtkwave step. Oscilloscope is great, pulseview great, but what's gtkwave doing here that the others can't?
Traubenfuchs 2y ago
The VanMoof e-shifter is awful: Every shift comes as an interruptive surprise which makes for a very uncomfortable ride. The test ride was the reason I did not get one. Cowboy bikes are much better, but mine broke on the second day. I sent it back. Now I got big legs thanks to those brittle novelty iPhone e-bikes failing me.

47 points by jandeboevrie 2y ago

> The reliability of this e-shifter in the X3 and S3 has been argued as the cause of the failure and eventual bankruptcy of VanMoof I always wondered what exactly the problem e-shifters were trying to solve was. Is it the "ugliness" of shifting cables? Route them through the frame...

morsch 2y ago
I doubt it's about the cabling. It's convenient not to have to think about shifting, like an automatic transmission in a car. I sometimes wish my bike had it.
- amluto 2y ago
  Good luck. With a derailleur, no amount of e-shifting magic can shift while stopped. And even with a hub shifter, most “automatic” systems I’ve used have an annoying failure in which you slow or stop briefly, try to start pedaling again, and discover that the system has chosen that moment to downshift several steps and you actually can’t go anywhere until it’s done.
  - morsch 2y ago
    Yeah, I'm not holding my breath.
mtts 2y ago
Regular shifter cables can and are also routed through the frame. Expensive road bikes (as well as the ones professionals ride) use e-shifters without any problems. These are made by companies that have some expertise in manufacturing shifters. They’re very expensive, though, as they’re made for road racing, not for regular bikes like the ones VanMoof made. VanMoof wanted to do everything themselves and found out the hard way that was a bad idea.
ndsipa_pomu 2y ago
I've got Shimano Di2 shifters on my road bike and they're very luxurious to use. Advantages: The controls are simply electronic switches, so you don't need much finger strength to operate them (reputedly these make them useful for people with hand strength issues such as arthritis) and also this means that you can reconfigure them (e.g. a one-armed cyclist can move the relevant controls to just one side) or even add extra controls such as sprinter buttons. If you've got double/triple chainrings, then the gear change can incorporate the switch-over point so you can just change up or down a gear and let the electronics handle when the chainring shift should occur (this can be changed in the software too according to your preferences). Also, with regards to the chainrings, the shifting system can adjust the front derailleur to accommodate the chainline better i.e. the front derailleur may need to be a mm or two further over for the smallest or biggest rear cog to prevent the chain rubbing. That's commonly referred to as "trim" and can usually be done manually on a manual gear system. Probably the biggest benefit is highly reliable shifting - once set up, it will perform perfect shifts every single time, whereas traditional gears will need adjusting as the gear cable inner stretches over time. As to disadvantages, the biggest issue is the price and the next problem would be that you need to keep the battery charged up or otherwise you're not going to be able to change gear. Typically, a single charge will last for thousands of shifts or a few months. I've also had the battery fail and unfortunately, they're very expensive to replace as the battery component also houses the main electronics for the system (e.g. the brain).
- mcntsh 2y ago
  An indexed shifter can also perform perfect shifts for thousands of times, and after that time you don't need to change out a battery you just need to maybe turn the barrel adjuster a few mm. The chainring thing is cool but front-gearing is also sort-of on the way out in favor of 1x groupsets. One of the greatest things about bikes, IMO, is how elegantly simple they are and how that translates into reliability and ease of maintenance. The push to using electrical components feels like a step in the wrong direction in this regard.
  - analog31 2y ago
    Note that the VanMoof was an e-bike with a lot of built-in features, so it wasn't intended to attract a minimalist market in the first place. The point is, it's an everything bike, in a stylish package.
analog31 2y ago
Trek Lime had an automatic 3-speed, circa mid-2000's. A friend of mine had one. I don't think there were ever widespread reliability issues. Sram had a 2-speed automatic that was fully mechanical.
tonyedgecombe 2y ago
My wife struggles with shifting gears so an automatic shifter would make things easier for her.

cubeflake 2y ago

Nice write up! I am also fiddling with my bike and have just figured how to pull the binary from the main M4 soc. Perhaps you could share your work with https://github.com/Bernardus/openmoof https://github.com/Bernardus/openmoof (Not my repo but has a lot of good info, I plan to share the binary as well once I made some progress in reversing it)

vr46 2y ago

Intriguing stuff here from a geek perspective, as I have an X2 and am only plagued by a lack of gears. I would expect e-shifters to have been made reliable by the time the 3 series came out, I didn't realize they were that bad, especially as I would love to see them everywhere. Having to adjust my son's bike shows how tough shifting gears can be, and the cable is constantly stretching. Plus, the whole getup freezes in winter.

Neywiny 2y ago

Can the second analyzer software not do the same measurement as the first? Coming from a point of ignorance here: I lucked into some higher and DLAs (though not 5v compatible so they wouldn't directly help here) and their softwares allow both decode and measurements

crote 2y ago
Yes, but only in hindsight - and you have to take the "part 1" into account too. An oscilloscope is able to show analog values. If you have no clue what a signal is, it is your best bet to start with. In this case it turned out to be a simple digital serial signal, but it could've just as well been a 0V-5V analog one or perhaps an open drain bus with pullups like i2c. Logic analyzers only really work for binary values. You are able to set a single threshold: everything above becomes a 1, everything below becomes a 0. Great if you've got a purely digital signal, useless if it has analog components. In the first part the author had to start with an oscilloscope to begin exploring. They could've probably switched to the logic analyzer before the first step of part two, but there isn't really a strong reason to do so - and there would still be a nonzero chance of analog components playing a role. Seeing that it was a simple digital "one wire TX, one wire RX" probably gave enough confidence to assume it was something like serial uart and move on.
- Neywiny 2y ago
  Maybe I wasn't clear enough, I meant cutting out the gtkwave step. Oscilloscope is great, pulseview great, but what's gtkwave doing here that the others can't?

Traubenfuchs 2y ago

The VanMoof e-shifter is awful: Every shift comes as an interruptive surprise which makes for a very uncomfortable ride. The test ride was the reason I did not get one. Cowboy bikes are much better, but mine broke on the second day. I sent it back. Now I got big legs thanks to those brittle novelty iPhone e-bikes failing me.