Special Issue

[MuddyWaiter]

My own problem. Not anybody's fault. But in my case, I found that my OWN code using the nI2c library (excellent!) did not seem to make the pull-ups engage on my DMStrong Mega 2560. I had to remove two resistors from this board to get I2C to work at all in the first place! The device in question is the BME680. It works correctly when I add 2 4.7k pull-ups. But without them, it WORKS with a Wire library example, and not with yours! This mystery is puzzling to me. I'm a bit of an amateur, but I think I've found something important. Perhaps you can shed some light on this? I've been successful with these DMStrong units already before. I have a scope. I was also wondering if I can access nTWI functions. I'm also kind of new to C...

[Amitesh Singh]

i think it's due to internal pull up enabled at this line
https://github.com/nitacku/nI2C/blob/master/nTWI.cpp#L48

You could just comment out these two lines and then it would work with external pullups as well.

[MuddyWaiter]

[Solved]This tricky sensor required careful research of the mfgr. pdf.FYI (and the world), my work was based on the simplified "Zanshin" Arduino C source for the BME680.First the pdf says that it has a .33hz update. So we're calling it too often. Should be every 3 sec.2nd, it really IS a 3.3v sensor. So, level shifters.Last, and MOST important, there's a BAD assumption in Zanshin's source (no offense):Every time we take a reading, the sensor has to be told to take the next one. This involved a classic Read-Modify-Write method that ASSUMES PERFECT I2C communication. One bad read, and the register written back to the device put it into an UNDEFINED state of operation.  I changed the code to always write the mode we selected at startup instead of getting it from the device each time.BTW: I've really come to like nI2C. I'm using it with a hardware watchdog IC, and was glad that your code was understandable enough to add brief calls to my ClrHWWdt() function so I could increase the timeout variable value.Thanks!On Jan 29, 2021 2:56 AM, Amitesh Singh <[e-mail]> wrote: i think it's due to internal pull up enabled at this line https://github.com/nitacku/nI2C/blob/master/nTWI.cpp#L48 You could just comment out these two lines and then it would work with external pullups as well. —You are receiving this because you authored the thread.Reply to this email directly, view it on GitHub, or unsubscribe.