Hello. We’ve previously used the SparkFun RFID Qwiic Readers without issue, but are struggling with undercounting RFID scans and occasionally scanning an nonexistant (repeated identical - 3102000232) tag across multiple devices.
We have not changed anything about the code or build, but did notice that in our most recent batch of RFID Qwiic Readers, the addresses were changed (we’ve updated these from 7D/7C to 13/14 in our code accordingly and detect the readers just fine). It looks like new firmware was also updated on these new readers.
What is different about the 2 readers so that we can better troubleshoot our issues?
Alrighty - have you disabled all but one set of pull up resistors on the i2c bus? You accomplish this by severing the traces labeled “i2c” in this photo (using an exacto knife or similar), be sure to leave only one set intact and re-try
Ah, when we tried that previously, we severed those jumpers on BOTH readers. We will try that tomorrow and let the systems run overnight and get back to you.
We are trying the I2C jumper modifications on one of the boards currently. But now that I’m back in the office I was able to look at the chips on the “old” (7D/7C addressed reader) vs “new” (13/14).
The new readers read:
ATMEL355B2B
TINY84-20U
231016U
The old readers read:
ATMEL355B2B
TINY84-20U
2230TEH
So they boards are physically different. I’m assuming the last number is referencing a batch number? Might this have a different firmware on it?
EDIT: sorry I flipped the bottom lines on the boards. It is corrected now. 7/24/25
@michaelheiml82 I’ve actually been in contact with @happy_kass about this and unfortunately they are different issues, BUT I’m guessing they stem from the same source.
We only ever see 1 unique false RFID that reads <10 times in 24 hours, so it doesn’t sound as extreme an issue. However, we previously did not have this problem, so we’re trying to get down to the bottom of it.
We are daisy chaining 2 scanners together, and we’re currently testing cutting one set of I2C jumpers on a reader to see if this resolved our issue, per Russel’s suggestion. I can keep you updated.
@TS-Russell maybe Sparkfun could sell us boards with the updated ATtiny84 firmware? We are woking with multiple boards so updating it in house will be difficult and we will end up damaging the boards
The last set of numbers on the chip are a date code for when the chip was manufactured in YYWW format. YY is the year, WW is the week in that year.
Not sure what the last 3 characters in the date code are but the datasheet for that chip will tell you. (Probably what facility or production line within the facility made them)
Unfortunately disabling all but one set of pull up resistors on the I2C bus did not resolve our issue. It actually appears to have made it worse on some of our systems.
Thank you for looking into the reader stock! What I’m experiencing is consistent with @happy_kass and @michaelheiml82 thinking it’s a firmware issue.
