Orchard EVT1 to DVT1

ECO1: Fix Microphone mirroring

Microphone schematic symbol was mirrored. No BOM change, board layout change only.

ECO2: Make battery easier and safer to solder

Space battery terminals wider, increase pad size, and add solder mask openings around the battery tabs. This makes it less likely to short wires together during a botched soldering operation.

ECO3: Fix gas gauge topology

Gas gauge goes between the charger and battery, not between the charger and the system. Oops!

ECO4: Add isolation resistors on SPI to OLED

For independent I2C operation of the OLED and complete dedication of the SPI bus to BLE, isolation resistors are needed on SPI1_SCK and SPI1_MOSI to the OLED display.

EVT	DVT	Notes
added	R19D 0 ohm
added	R20D 0 ohm

ECO5: Add USB adapter presence logic

There is no reliable way to detect the presence of a USB power source due to the VUSB boost mode supply of the BQ24260 (observing VUSB isn't helpful because BQ24260 supplies it when the USB power is disconnected).

Add a 10k ohm pull-up resistor to USB_P and a 100k pull-down resistor to USB_N. Wire USBD_P via a 0-ohm jumper to a spare ADC input on the Kinetis-W.

Expected behavior:

• When no USB host is attached, USB_P goes to 3.0V
• When a USB host is attached, USB_P is pulled down to somewhere around 2.2V
• When a USB dedicated charger is atached, USB_P is pulled down to around 2.8V
• The only failure case is if the charging source has no resistors or other indication on the D+/D- lines.

A software loop will need to sample the USB_P pin and toggle between boost and charge mode.

EVT	DVT	Notes
added	R29B 10k, 1%	pull-up on USB_P
added	R31B 100k, 1%	pull-down on USB_N
added	R30B 0 ohm	allow spare ADC input on Kinetis-W to sample USB_P

ECO6: Improve boost ripple performance

Add another 10uF cap on VUSB to improve ripple performance during boost mode.

EVT	DVT	Notes
added	C28B 10uF, 10V X5R	}