wiken
New Member
Posts: 45 
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Post by wiken on Feb 1, 2019 10:00:00 GMT
Hi. Just a gentle reminder about I2C bus. This is probably known to all out there.
I'm rewriting an Arduino Due application to a TC275 ShieldBuddy.
Arduino Due has internal pull-ups on SDA(20) and SCL(21), but not on SDA1 or SCL1. TC275 has no pull-ups on these pins, so you need to add from 2.2 to 4.7KOhms on each pin to 5V, or 3.3V.
When the Master(TC275) is sending a NACK to the device it just releases the bus, and the two pull-ups are generating that NACK. If you are missing those resistors, you get a TRAP generated at interrupt-release, if you read the I2C in a loop.
\Wiken  |
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Post by hobie1978 on Feb 1, 2019 11:39:47 GMT
Hi Wiken,
it's been a while since I was experimenting with the I2C port.
I'm building the hardware to mount my electronics on (an old tractor with a newer Mercedes engine for tractorpulling).
I haven't used resistors until now, but I hooked up about 6 or so Arduino Nano clones.
Requesting around 24+ variables in total for 50 to a 100 times a second.
The only thing I experienced was that every X request was a bit slower, total transfertime was 10 to 20% longer.
I'm designing the PCB's which have room for resistors.
When the pcb's are ready I put the scope on and see what if I can make it better.
But still a lot of work.
Regards Johan.
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