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High Speed I2C sensor with 9V 
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Post High Speed I2C sensor with 9V
Hey guys,

I am keen to test my HiTechnic Proto board with a higher I2C speed. I know it's not supported by HiTechnic at that speed, trust me, I will not ask for support from them if it fails to work. However, I need to know what sensor type to use. I am currently using sensorI2CCustom9V. Which one is the high speed cousin of this one?

I am using RobotC 1.40 Public.

Regards,
Xander

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Thu Aug 28, 2008 4:16 pm
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Post Re: High Speed I2C sensor with 9V
Use "fast, skip states, 9V'. It works fine for me.

HiTechnic is a little "gun shy" because of a now fixed bug where I2C clock and data were being changed in the same "time slice" and with long sensor cables even though clock was being changed before data line by a few tenths of a microsecond, the HiTechnic sensor was recognizing the data line change first. This causes the HiTechnic (or any other sensor) to "reset" I2C messaging. The problem has something to do with capacitance on long sensor cables. ROBOTC firmware was fixed to ensure that these two signal transitions occur in different time slices; the problem still exists in the standard LEGO firmware


Wed Sep 17, 2008 9:46 pm
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Post Re: High Speed I2C sensor with 9V
Hiya Dick,

I've been speaking with Steve from HT (and I am sure you have, too) and I ran some tests by writing an incremented value to an unused register and then verified it by reading it back 1000 times. So in all I did a little over 250 writes and 250000 reads and not a single error. Also the speed at which the reads were done was consistently 500 per second. So for now, it seems the NXT is "limited" to 500 I2C transactions per second. I also noticed no difference in the total number of transactions per second between a request for a single byte or two byte reply. That means you can query a 12 bit ADC as many times per second as an 8 bit one!

Regards,
Xander

_________________
| Professional Conduit of Reasonableness
| (Title bestowed upon on the 8th day of November, 2013)
| My Blog: I'd Rather Be Building Robots
| ROBOTC 3rd Party Driver Suite: [Project Page]


Thu Sep 18, 2008 2:15 am
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