This is a page to keep track of our PCB revisions, document design changes, and receive feedback.
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- Remove extra regulator circuit (Kevin's), source smaller crystals, make all resistors and LEDs 0603
- Fix trace lengths for crystals
- Reverse voltage protection? Decided not to implement on controller as the 12V connector will be on carrier board
- Fix all footprints to match the Hardware Style Guide Rules & Guidelines - Still in progress
- Replace board info silkscreen as directed in the Hardware Style Guide Rules & Guidelines - Incomplete, will do for next rev
- Connector changes:
- Combine SWD and UART headers (we may be able to hack the programmers to also be UART to USB adapters) or replace them with prototyping headers - Used 6 pin SMT 0.1" header
- Replace 12V connector with test points - Decided not to use test points as the regulator has already been tested (decoupling caps can be used as test points)
- Replace mezzanine connector with 0.8mm pitch equivalent to increase lifespan and verify mating height - 0.5mm pitch connectors need to be tested first, then consider this if necessary
- Change all connector part numbers to vertical connectors
- put male side of mezzanine on controller board
- Add guide holes for mezzanine footprint
- Signal connectors switched to Duraclik
- Silkscreen pinout for connectors
- Reduce induced ripple on 12V rail - Test with different input caps
- Improve ripple behavior on 3.3V rail - Will test with different output caps
- Calibrate regulator to 3.3V (currently at 3.36V) - Shouldn't be a big issue
- Get stencils
- Lower blue LED brightness (spec an LED ), raise green LED brightness
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- Used reflow oven + stencils - turned out very well once we created a stencil jig with spare boards and tape!
- Stencil jig is essential - need to deposit the correct amount of solder paste, especially with
- Ripple is better, not as great as we hoped - ripple greatly reduces at loads > 100mA
- 89mV peak-to-peak variation at light loads vs. 29mV at 100mA in ADC testing - ELEC-
- LED brightness is good
- Might want to switch debug UART to USART3/4 - USART1/2 seem to have more features
Revision 4
Design Changes
- Remove some of the output filtering on the 3v3 regulator
- Add 3V LDO for analog components - shared ground should be fine
- Move test points a little farther away from the mezzanine?
Revision 5
Design Decisions
- Replaced EOL regulator with RECOM Power E-series DC-DC
- Replaced horizontal DuraCliks with vertical variants to allow for more flexibility in carrier boards
- Removed 32kHz crystal under the assumption that we would never use the RTC or CRS
Retrospective
- Regulator + diode works well, VCC is around 3.18V
- The resistor array was a little difficult to solder by hand, but overall the board didn't take too long even without hot air
- Need to check ripple on 12V, VCC, and VDDA.
Revision 6
Design Change
- HSE is connected to the wrong pins (turns out it's been that way since before Rev 4)
- PCB layout was modified to fit the CAN connectors next to each other
Retrospective
- HSE is now functional on OSC_IN and OSC_OUT
- Using hot air to reflow the CAN connector side made it a lot easier, although it's easy to overheat the duraclik connectors so it may be easier to do those by hand later
- Reflow can be used to solder the RECOM DC-DC module on, doing it by hand led to poor connections on one of the boards (now fixed)
- 12V, VDD, VDDA should be characterized
- MCU's built-in ADC needs to be characterized
- Resistor array for the debug LEDs should be on the top side (if possible) to avoid soldering
- Power supply has a very larger footprint
- Decoupling capacitors for the crystal are not selected based on the recommended equation