PCB suggestions

Posted by Pilkerton on May 22, 2016; 4:17am
URL: http://bluesaab-forum.90.s1.nabble.com/PCB-suggestions-tp411.html

The BOM <-> schematic mismatch tripped me up when I assembled a v3.3a board from the Mouser BOM:

Current BOM       Schematic                                   Customer Part # on BOM should change to
-------------------------------------------------------------------------------------------------------
U2 Socket           U1                                              U1 Socket
IC2                     U3                                              U3
IC1                     U2                                              U2
U2                      U1                                              U1
RN52                  U4                                              U4
LED1-4               BT1, CAN1, CAN2, POWER            BT1, CAN1, CAN2, POWER
-------------------------------------------------------------------------------------------------------

Recommendations for future PCB revs:
• 'IC3' should ideally be 'U5', but this would require schematic and silkscreen changes
• Top side silkscreen should somehow indicate polarity for all LEDs
• Square pad for Atmega U1 pin 1
• Bottom side silkscreen alignment marks near RN52 pins 1 and 44 should be moved out slightly to help 'frame' the component during placement; currently, these marks are obscured when the part is in place.

Other thoughts:
• Is the Mini USB connector really necessary? It's exclusively for RN52 firmware updates, but as of RN52 firmware v1.16, it defaults to updates over the UART pins. Also I was unable to get the update utility to communicate with the RN52 in DFU mode over USB using Windows 7 64-bit.

• Why not switch to an SMT package for the Atmega? It seemed like I spent a disproportionate amount of time soldering that single DIP package.