Monday, 14 September 2015

More PCBs (6500 Rev. B)

I finally got around to fixing any problems that I found with my first set of boards (which actually wasn't anywhere near as many as I expected!), so here is revision B:

(again, ignore the silkscreen date/rev C - I forgot to take a screenshot before changing the text)

Which might look ok at a first glance... except they thought they knew better than me about what I wanted fabricating and decided to mess with my design files! They handled it well though and even though I sent just a polite query, they accepted responsbility for it and gave me around a 25% credit which was nice. Some details of the changes at the end of this post.

Spot the difference(s) (or scroll down for the list):

Something that I haven't seen / isn't written about in anything that I've read so far is how handy UV reactive flux is. These were after cleaning with IPA and a brush!
It's not easy to photograph though, and looks much better/clearer IRL.

After cleaning it a couple more times, smoke test time... and nothing. After I had re-done most of the power bits I shouldn't have been surprised! After much probing and confusion it turned out to be a faulty/damaged USB mux and not my design. Maybe caused by the fact that they arrived loose in a plastic bag, with styrofoam padding, and then clingfilm around it :/ Anyway, replaced that and it worked OK:

2015-09-13T02:31:18 INFO src/stlink-common.c: Loading device parameters....
2015-09-13T02:31:18 INFO src/stlink-common.c: Device connected is: F2 device, id 0x20076411
2015-09-13T02:31:18 INFO src/stlink-common.c: SRAM size: 0x20000 bytes (128 KiB), Flash: 0x80000 bytes (512 KiB) in pages of 131072 bytes
2015-09-13T02:31:18 INFO gdbserver/gdb-server.c: Chip ID is 00000411, Core ID is  2ba01477.
2015-09-13T02:31:18 INFO gdbserver/gdb-server.c: Target voltage is 3227 mV.
2015-09-13T02:31:18 INFO gdbserver/gdb-server.c: Listening at *:4242...

Back to the changes they made:

- No soldermask between pins


- Randomly decided to add some soldermask where there was not supposed to be any

...and just on one as well, the rest went unmodified!

I tried to remember to note any changes that I made, although there will be some I missed. Here's the list:

- Annotated more stuff
- Added missing TPs for I2S SPK out
- Fattened cap traces for mag sensor (datasheet advice)
- Removed via and copper from under mag sensor (datasheet advice)
- Rearranged traces under FPC connector for better ground plane
- Neatened up a few uneven tracks
- Rotated text on bottom silkscreen
- Swapped PIC pins 1&6 (6 can only be an input)
- Fixed volume switch pinout
- Moved USB capacitor a tiny bit
- Increased BOOT1 pull-down to 10k
- Added footprint for SOT23-5 EEPROM (in addition to SOIC)
- Added SJs for non-essential IC power (NC)
- Added xtal (DNF) for I2S, and routed MCLK to XIN
- Added resistor divider as a battery charge measuring test
- 1k5 USB DP resistor (oops...), and pre-biased PNP switch
- 2mm pads for ext V_IN
- GND RFU to ease transition to F4xx
- 100k pull-ups on SD unused DAT pins
- Diode footprints changed to SOD-323
- Swapped a few tantalums for ceramics
- No mask around top back mount holes
- Re-routed 3V3
- Changed JTAG connector to 1mm pitch JST 8-pin
- Added power switch
- Added a missing decoupling cap
- Routed HP audio to USB MUX
- Replaced PIC with a PNP transistor inverter - CBA
- Had to go to 6/6 for top keypad, I2S, and some others
- MCU decoupling caps down to 0402

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