BioCell Subsystem Build & Test
Table of Contents
Vision for Biocell Subsystem Level Build & Test Phase
During this phase, it was the goal of the BioCell team to complete the design of the BioCell, populate the hardware components and begin basic functionality testing (power-up, device communication, etc.) Additionally, it was the goal to begin writing the software drivers.
The team was successful in meeting the aforementioned goals. Functionality testing was a success and communication was transferred over the I2C bus to the BioX cell's temperature, humidity, and pressure sensors. Additionally, the I2C LED drivers were used to enable the growth and flash LEDs.
Test Results SummarySeveral of the defined test plans were successfully completed and evaluated over the past phase. This includes: PCB power-up and evaluation, I2C bus communications, and evaluation of the provided Light power. The test plans, as well as those remaining to be evaluated, for the BioCell can be found in BioCell Individual Test Plans.
An example of a completed test plan is shown below. This test plan describes the steps and procedures needed to evaluate the Growth LED availability. Through the I2C serial protocol, the device was successfully reset, and the LEDs were enabled by driving the respective inputs to ground and enabling the internal oscillator. This test successfully demonstrated the ability to communicate with the LED driver, and drive the LEDs. This was completed for the two sidewall PCBs and the flash PCBs.
With this same test, the current draw of the LEDs could be evaluated thus allowing the Light power delivered to the cell to be understood. Each sidewall conducted 220-240 milliamps under full load at 5V. Given the square area of the eventual cell, it was determined that 343W/m2 would be delivered, well within the range of what is expected and meets the nominal value. The current draw of the LEDs is shown below.
Visible verification was completed for the flash PCB. Total power has not been calculated because of faulty LEDs. To verify that the infrared LEDs were enabled, a thermal imaging camera was used. With the known location of the infrared LEDs and the emitted energy in these locations, it was concluded that 3 of the 4 infrared LEDs are operating correctly. This is demonstrated below in the functional demo section.
Finally, with a serial analyzer, communications were established with the pressure, temperature, and humidity sensor. Very basic routines were written through an Arduino to verify the proper functionality and validity of each sensor. An example of one such communication is shown below. This particular communication requests a read of the humidity sensor's status register.
Risk and Problem Tracking
We are currently tracking three issues:
- The current BioCell structure is not able to maintain pressure. A new design has been planned but is yet to be tested because focus has shifted to the entire structure. [IN PROGRESS.]
- The Flash PCB was designed with an incorrect orientation; that is, the top of the PCB in the schematic editor was meant to face down in the BioCell not towards the top of the cell. This directly affected the LEDs because they were not pointed towards the plant as intended. This is fixed by reversing the order of the LED and the resistor for each input. [SOLVED.]
- The MSP432P401M may not support the memory requirements needed (64kB). However, the MSP432P401R offers twice the memory and fits in the same 64-pin package. This solution is currently being evaluated. [IN EVALUATION.]
Functional Demo MaterialsTo demo the functionality of the BioCell, the functionality of the sensors and LED drivers will be demonstrated through an Arduino program.
Verification of the infrared LEDs can be see below. There is one infrared LED not fully on in the bottom left corner of the PCB, but the remaining are believed to be fully on.