Stacking Arduinos

Hi all,

I can't find any particular solution to this problem. I have a project that utilizes 2 Ardiuinos (Arduinii?) communicating via I2C. The project works fine, though when I tried to compactify the hardware, I came up with the idea of stacking the Arduinos with the stackable headers from Adafruit or wherever, though I only connected one side. The following pins are connected: Reset, 3V3, 5V, GND, GND, VIN, and analog0-5. All the digital pins and the RX/TX are NOT connected. My problem is that I can no longer upload software to the boards. I have to physically separate them in order to upload. This is annoying, since it means opening the case, disconnecting and removing the arduinos, unscrewing all the standoffs, uploading software, and then putting it all back together. How come I can't program them when they're stacked?

That’s odd. What Arduinos are these specifically? Anything unusual about how they are powered or programmed? Is this programming over USB? If not, what programmer are you using?

I’m wondering if the load on the RESET line (double the load, that is) is preventing the auto-reset process from working correctly. Is there any way you can stack them with the RESET pin sort-of not connected (just bend it out a bit)?

The Flexible MIDI Shield: MIDI IN/OUT, stacking headers, your choice of I/O pins

I was thinking the same - whatever is pulling reset low can't drive the 5K pullup that results from 2 10Ks in parallel

The reset connection was the problem. I cut that connection and everything worked out.