Consider enabling SPI MOSI as transmit line

[joulesverne]

For most TI MSP430 MCUs, SPI out line can be used as an AWG, facilitated by a SPI Tx interrupt triggered DMA transfer.

Consider providing a population option which routes one of the SPI MOSI to the transmit switch control line.

[MaineTree]

2 options, recommend option 1:
1. jumper select with currently unused UART
2. jumper select with SPI for peripherals

UART is not currently used in any WISP6 firmware on cursory inspection. Current focus is on accelerometer and camera that will not use UART.

For option 2 peripheral sharing is ok but adds line capacitance to the ADG902 control line, this seems like a sensitive line we shouldn't touch. Also means more complexity managing shared resources in firmware.

Placement and routing should be workable. Several traces will need rerouting to make room for 2 x 0402 0 ohm jumpers.

Changes to be made:

• Add DNP resistor to select MCU pin 38 (GPIO) or pin 20 (serial peripheral)
  • Move current 0 ohm on ADG902 control (R28) to MCU schematic for GPIO pin select option
• Place and route R28 + additional resistor

Picture of rough area of UART TX signal where 0402s could be placed with adjustment

@joulesverne Confirm if you'd like this change

[joulesverne]

Yes... unless this opens up a can of worms as you're implementing, let's go for your option 1 above!