It all started a couple of years ago. I bought an excellent JTAG programmer from Distortec.
It worked perfectly, until one day, where I could not figure out what was wrong.
I kept messing with software and setup, and finally I found out that the problem I had was because I had changed my cable connection to the adapter.
There was nothing wrong with the adapter.
It seemed like I had a defective USB cable.
...Or did I ?
I had bought a bunch of nice-looking short USB cables from China on eBay. Don't buy those cables. The shop is fine, but this particular kind of cable isn't.
I tried measuring the resistance in the short cables, and to my horror, the resistance was much higher than the long USB-cable that came with the JTAG adapter from Distortec.
Hmm. more than 2.0Ω resistance on a 65,5cm cable against 0.4 Ω on a 202cm cable.
I decided to try buying cables from different places.
On eBay, I found a store called kenable_ltd. I decided to buy a couple of cables there; in the hope that they would be working better than the China-cables.
I also bought cables from a few other places on eBay.
When the Kenable cables arrived, I tried them; they worked. These were short 50cm USB2-A to Mini-B cables. I tried measuring their resistance on each wire, and got surprised that the resistnce was so low.
The other cables also arrived; they were not as impressive, but still working well. Looking up the rules for USB-cables, I found out that many cables are near the allowed limit for USB2.0
But it seems that the USB-cables from Kenable are the best possible quality. So I've decided to buy from them from now on.
Now I buy directly from Kenable's Web-shop instead of buying via eBay.
I also measured all the cables I received on the last shipment, and wrote the results in the table below.
I hope this Web-site will help a few people out there realize that "a wire" is not just "a wire", but the quality can really make a difference.
Now being fond of Kenable, I would also like to mention that they ship the order quickly, and from UK to Denmark it takes the mailman usually 4-5 days to get here, sometimes less. I hope he had a nice trip. ;)
It worked perfectly, until one day, where I could not figure out what was wrong.
I kept messing with software and setup, and finally I found out that the problem I had was because I had changed my cable connection to the adapter.
There was nothing wrong with the adapter.
It seemed like I had a defective USB cable.
...Or did I ?
I had bought a bunch of nice-looking short USB cables from China on eBay. Don't buy those cables. The shop is fine, but this particular kind of cable isn't.
I tried measuring the resistance in the short cables, and to my horror, the resistance was much higher than the long USB-cable that came with the JTAG adapter from Distortec.
Hmm. more than 2.0Ω resistance on a 65,5cm cable against 0.4 Ω on a 202cm cable.
I decided to try buying cables from different places.
On eBay, I found a store called kenable_ltd. I decided to buy a couple of cables there; in the hope that they would be working better than the China-cables.
I also bought cables from a few other places on eBay.
When the Kenable cables arrived, I tried them; they worked. These were short 50cm USB2-A to Mini-B cables. I tried measuring their resistance on each wire, and got surprised that the resistnce was so low.
The other cables also arrived; they were not as impressive, but still working well. Looking up the rules for USB-cables, I found out that many cables are near the allowed limit for USB2.0
But it seems that the USB-cables from Kenable are the best possible quality. So I've decided to buy from them from now on.
Now I buy directly from Kenable's Web-shop instead of buying via eBay.
I also measured all the cables I received on the last shipment, and wrote the results in the table below.
I hope this Web-site will help a few people out there realize that "a wire" is not just "a wire", but the quality can really make a difference.
Now being fond of Kenable, I would also like to mention that they ship the order quickly, and from UK to Denmark it takes the mailman usually 4-5 days to get here, sometimes less. I hope he had a nice trip. ;)
| Cable name | Order code | Actual length | Total Resistance | Resistance per meter | Score | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| (in cm) | GND | D- | D+ | VCC | GND per m | D- | D+ | VCC | (limit=1) | ||
| China Cables: | |||||||||||
| China USB2-A-mini-B-65cm | 65,5 | 2,90 | 2,20 | 2,50 | (open) | 4,43 | 3,36 | 3,82 | (open) | 0,00 | |
| China USB2-A-mini-B-65cm | 65,5 | 2,10 | 1,50 | 1,40 | 1,40 | 3,21 | 2,29 | 2,14 | 2,14 | 0,74 | |
| Distortec Cables: | |||||||||||
| Distortec USB2-A-mini-B 202cm | 202,0 | 0,40 | 0,40 | 0,40 | 0,40 | 0,20 | 0,20 | 0,20 | 0,20 | 10,10 | |
| Distortec USB2-A-mini-B 202cm | 202,0 | 0,40 | 0,40 | 0,40 | 0,40 | 0,20 | 0,20 | 0,20 | 0,20 | 10,10 | |
| Kenable Cables: | |||||||||||
| USB2-MINI-25CM | QS: 006877 | 26,0 | 0,10 | 0,10 | 0,10 | 0,10 | 0,38 | 0,38 | 0,38 | 0,38 | 5,20 |
| USB2-MINI-25CM | QS: 006877 | 26,0 | 0,10 | 0,10 | 0,10 | 0,10 | 0,38 | 0,38 | 0,38 | 0,38 | 5,20 |
| USB2-MINI-25CM | QS: 006877 | 26,0 | 0,10 | 0,10 | 0,10 | 0,10 | 0,38 | 0,38 | 0,38 | 0,38 | 5,20 |
| CDL-062-1.0 | QS: 002000 | 100,0 | 0,20 | 0,20 | 0,20 | 0,20 | 0,20 | 0,20 | 0,20 | 0,20 | 10,00 |
| CDL-062-1.0 | QS: 002000 | 100,0 | 0,30 | 0,30 | 0,30 | 0,30 | 0,30 | 0,30 | 0,30 | 0,30 | 6,67 |
| USB2-MINI-50CM | QS: 006878 | 50,5 | 0,15 | 0,15 | 0,15 | 0,15 | 0,30 | 0,30 | 0,30 | 0,30 | 6,73 |
| USB2-MINI-50CM | QS: 006878 | 50,5 | 0,15 | 0,15 | 0,125 | 0,15 | 0,30 | 0,30 | 0,25 | 0,30 | 6,88 |
| USB2-MINI-1.8M | QS: 001999 | 180,0 | 0,40 | 0,40 | 0,40 | 0,40 | 0,22 | 0,22 | 0,22 | 0,22 | 9,00 |
| USB2-MINI-1.8M | QS: 001999 | 180,0 | 0,40 | 0,40 | 0,40 | 0,40 | 0,22 | 0,22 | 0,22 | 0,22 | 9,00 |
| WHITE-USB2-EXT-50cm | QS: 006868 | 51,2 | 0,11 | 0,10 | 0,13 | 0,13 | 0,21 | 0,20 | 0,25 | 0,25 | 8,81 |
| WHITE-USB2-EXT-50cm | QS: 006868 | 51,2 | 0,11 | 0,115 | 0,12 | 0,12 | 0,21 | 0,22 | 0,23 | 0,23 | 8,95 |
| WHITE-USB2-EXT-50cm | QS: 006868 | 51,2 | 0,11 | 0,11 | 0,11 | 0,11 | 0,21 | 0,21 | 0,21 | 0,21 | 9,31 |
| WHITE-USB2-EXT-50cm | QS: 006868 | 51,2 | 0,11 | 0,10 | 0,12 | 0,12 | 0,21 | 0,20 | 0,23 | 0,23 | 9,10 |
| WHITE-USB2-EXT-1m | QS: 006866 | 100,5 | 0,22 | 0,23 | 0,20 | 0,22 | 0,22 | 0,23 | 0,20 | 0,22 | 9,19 |
| WHITE-USB2-EXT-1m | QS: 006866 | 100,5 | 0,23 | 0,23 | 0,19 | 0,23 | 0,23 | 0,23 | 0,19 | 0,23 | 8,93 |
| WHITE-USB2-EXT-1.5m | QS: 006869 | 150,7 | 0,33 | 0,35 | 0,30 | 0,34 | 0,22 | 0,23 | 0,20 | 0,23 | 9,10 |
| WHITE-USB2-EXT-1.5m | QS: 006869 | 150,7 | 0,33 | 0,34 | 0,34 | 0,34 | 0,22 | 0,23 | 0,23 | 0,23 | 9,00 |
The above tests were made using calibrated equipment, so only the actual USB cable resistance is measured. Each wire is measured individually.
It is important that the GND wire has low resistance; preferrably lower than any of the other wires, including VCC.
It is also important that VCC has a low resistance. The Data lines are the least important; and the resistance on these is allowed to be slightly higher than both GND and VCC.
The table shows that not only is the cables I bought in China using low quality wires, they aren't soldered properly either.
It is important that the GND wire has low resistance; preferrably lower than any of the other wires, including VCC.
It is also important that VCC has a low resistance. The Data lines are the least important; and the resistance on these is allowed to be slightly higher than both GND and VCC.
The table shows that not only is the cables I bought in China using low quality wires, they aren't soldered properly either.