Solar Driveway Light to MSP430 Wireless Sensor Node

The basic idea of this project is to convert a $3-4 solar light found at Lowes and Home Depot hardware store (here in the US) into a wireless remote sensor node.  The node will utilize an MSP430G2553 MCU and a nRF24L01+(w/ spirilis library) wireless module to send light intensity (photoresitor that came with solar driveway light), soil moisture (design from, and soil temperature data (10k thermistor coated in silicon) wirelessly from my garden to another MSP430G2553 and nRF24L01+ sitting on top of a Raspberry Pi.

Solar Driveway Light to MSP430 Wireless Sensor Node

This data will then be sent over the Raspberry Pi UART to a python script running on the Raspberry Pi which logs the data into a CSV and JSON file (code inspired by Uberfridge).  An Apache server will also run on the Rapsberry Pi and the JSON data will be displayed via the Javascript Flot chart library.  The node on the Raspberry Pi will also have a transistor that switches a water Solenoid attached to my garden hose based upon the soil moisture.

I taught myself Eagle Autocad and created a schematic/board to replace the stock board inside the solar light.  My board utilizes a Texas Instrument TPS61097 (free sample) which converts the 1.2v from the batter to 3.3v to power the MSP430.  Version 1 of the board is shown below with just the power circuitry populated (Photo 6).

Solar Driveway Light to MSP430 Wireless Sensor NodeI put a jumper wire on the TPS61097 between the EN and VIN because I wasn’t able to get the bypass switch (Page 16 of the schematic…tps61097-33.pdf ) to work correctly.  I had 200k resistors on R1 and R2 (actually 2x100k 1% in series each…didn’t have any 200k on hand) which didn’t work (bypass switch stays on) so I jumpered EN and VIN and now get the full 3.3v.  I would like to get this bypass feature enabled.  Any ideas where I am going wrong here?  I assume the resistor values are incorrect for the 1.2v battery.


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