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Where Can I Find An Ez-b V4 I2c Peripheral Cable Longer Than 25 Cm?

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#1

I am building a 6" tall robot out of old Robotix parts and EZ Robot parts. I need a peripheral cable longer than the 25 cm one offered. Maybe 60 cm or so. Where would I find this, or do I have to just extend the cable by hand with individual wires?

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#2

You will have to cut and extend the wires. However, please note that there is absolutely no gaurentee the i2c device will work at that distance. I recommend using twisted pair at the least. The maximum bus length of an I2C link is about 1 meter at 100 Kbaud, or 10 meters at 10 Kbaud. You can adjust the i2c speed in the connection control settings within EZ-Builder. At that distance, you will certainly require a much much slower speed.

Bare in mind, slowing the speed of the i2c will also affect performance of the wifi connection. Because the slowest point will now be the i2c during i2c command send/receives via wifi

#3

Thank you for your response DJ Sures. My longest I2C connection will be about 40-50 cm away compared with the 25 cm cable that it comes with. Sorry as I am new to this but will I need to adjust the speed for this small change (as in cut the speed in half due to doubling the distance)? On another note, my HDD servos are as far away as 5 feet and my ultrasonic distance sensor is about 60-70 cm away. I already found the cables for those, but will I also run into problems here?

#4

Only the I2C will give issues with those distances. The protocol is very sensitive to cable length. The servos and ultrasonic sensor are much simpler and more fault tolerant. I am not an expert on I2C, but since it is distance sensitive I would assume it follows the inverse square law, so twice the distance, 4x lower speed for good success.

Does your bot have room for an IOTiny closer to where you need the I2C device? EZ-Builder can drive multiple EZ-B devices in the same project.

Alan

#5

The best way to find out is to try Grin

Twisted pair wire is used for Ethernet and long distance communication. I'd recommend cutting and extending the cable with the twisted pair. Once you get the cable created, the next step would be testing the i2c device with the speed divided by 2 (i.e. 50,000). Slowly increase the speed by 10,000 approaching the default speed of 100,000

Find a speed that works and you're rock'n

#6

Thanks everybody!