First, if I’m in the wrong place let me know.
I recently developed a custom PCB using the mega 2560 schematic. I’ve had to do a few modifications, but with the help of the AVR pocket programmer and the mega 2560 I’ve been able to burn the bootloaders. My PC is able to see the device as a mega 2560 and the IDE can see it as well. I’ve also been able to upload sketches via the AVR programmer. Now, I am unable to flash the atmega2560 via USB. The message below is what I get when attempting to upload via USB.
avrdude: stk500v2_ReceiveMessage(): timeout avrdude: stk500v2_ReceiveMessage(): timeout avrdude: stk500v2_ReceiveMessage(): timeout avrdude: stk500v2_ReceiveMessage(): timeout avrdude: stk500v2_ReceiveMessage(): timeout avrdude: stk500v2_ReceiveMessage(): timeout avrdude: stk500v2_getsync(): timeout communicating with programmer
While having both ends of the bridge, to me, the bridge between the atmega2560 and atmega8u2 is not existant. I am using a atmega8u2 instead of a 16u2. This is by accident in my BOM. That being said, I was able to use the AVR command line interface to burn a 16u2 bootloader the the 8u2. After not being able to flash via the USB i decided to upload to the atmega2560 using the ‘Upload using programmer’ option with no error. I used an i2c scanner sketch to see if I might see anything from the serial monitor. This proved to yield different results as seen in the attached ‘capture.jpg’ serial monitor output. This jumbled output appeared regardless of baud setting.
I thought I might be in error with the TX and RX lines. I have sat and compared my schematic (also attached) to the mega 2560 Rev 3 schematic and wasn’t able to find anything noticable.
Could this be a problem due to the fact that I am using an 8u2 instead of a 16u2? Perhaps resistor values problems of R104 and R105? I should also note that I received the wrong components for the varistors (Z100, Z101) and currently have them unpopulated. Would this also cause problems?
I’d really appreciate some guidance or any information. Thanks for your time.