![]() ![]() Use software I2C instead of the built-in I2C hardware.The reason that the R3 design has two new I2C pins is to accommodate bigger chips just because the Uno has the SCL/SDA pins connected to A4/A5 (because of the chip limitation) doesn't mean that that should be the case for an Arduino zero (in fact, I'm pretty sure it's not.) Not all AVR chips share the I2C pins and A2D pins, and some have more than 6 A2D to start with so it might not be a problem. 3) If you need 6 A2D inputs AND I2C, you have a couple options: ![]() If you want to use the I2C interface on a m328, you lose 2 A2D pins. ![]() 2) It is the Atmega328 chip on the arduino Uno (and similar) that shares pins between the hardware I2C interface and the A2D interface, and there's nothing an external shield or any amount of trace cutting can do to fix that. Huh? 1) I don't see any such claim for the "data logger shield." In fact, the board has only an SD socket and an RTC - the A2D converter is part of the Arduino board itself. use a triple SPDT switch 74HC4053 and one digital output to control it to switch six sensors into three ADC channels. The other option would be to fit an analog switch chip in the prototyping area and use one or more digital I/O line to control it to multiplex your sensors to the four available inputs. Check for continuity between the pads and all four header pins to make sure you have isolated it properly before reconnecting the shield to the Arduino. You can then patch the RTC's SDA,SCL pads (bottom left next to A5,A6 on the topside photo) to whichever pins you prefer for soft I2C. I would suggest *NOT* bending out pins but instead make the track cuts shown below. To free up A5,A6 for analog and isolate the RTC so you can remap it, you need to isolate it from both sets of pins as they are wired in parallel on the Arduino UNO R3 board. Which pins? Which tracks? The Adafruit data logger shield connects the I2C bus to the Arduino via two pairs of pins, A5,A6 on the analog in header, and SDA,SCL at the far end of the digital header on the other edge of the board. ![]() You said you bent out pins on the header and cut some tracks. ![]()
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