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5.1.7.5
Compute and Display Absorbance Workflow
The DLP Spectrum Library computes the absorbance of a scan based on the negative of the logarithm
(based 10) of the reflectance.
scanResults struct
(reference)
Intensity
Intensity
scanResults struct
Figure 5-6. DLP Spectrum Library Compute and Display Absorbance
5.2
Software System Overview
The DLP NIRscan Nano software uses a sets of tasks, hardware interrupts, and semaphores to
coordinate the efforts needed to interpret USB or Bluetooth commands, respond to button presses, scan
an object, and capture the InGaAs detector values.
software elements of the system. The DLP NIRscan Nano system includes the following hardware
interrupt handlers to respond to hardware events:
•
Button Interrupt Handler: Responds to Scan/Bluetooth button presses and Wake button presses.
•
Trigger Interrupt Handler: Synchronizes and keeps track of the pattern displayed during a scan. Two
interrupts from the DLPC150 (ihFrameTrigger and ihPatternTrigger) indicate when a pattern has been
displayed, when 24 patterns have completed the display, and when the DLPC150 buffer needs to be
reloaded with new patterns. This handler also captures data from the ADS1255 when a pattern is
displayed. It uses the ADS1255 DRDY signal to trigger the read of the just-converted value.
•
Display Interrupt Handler: Controls the Tiva LCD peripheral and its frame buffer that resides in external
SDRAM. The frame buffer streams 24 patterns per frame to the DLPC150.
The following tasks handle specific portions of the system:
•
USB driver: This task is part of the TivaWare USB driver and handles all USB HID transactions. The
data from USB transactions is passed to the command handler task to interpret and respond to a
specific set of USB commands described in
•
Bluetooth Stack: This task handles Bluetooth communication with a mobile application through the
implementation of GATT profile in the Bluetopia Stack. Several semaphores control the operation:
– BLEStartSem: Power-up the Bluetooth circuits and initializes the Bluetooth Stack.
– BLEEndSem: Powers-down the Bluetooth circuits and gracefully closes the Bluetooth Stack.
– BLECmdRecd: Coordinates the reception and processing of GATT profiles and notifies Command
Handler of a new command to be processed.
– BLECmdCom: Handles the response to a BLE Client's read and notify requests.
– BLENotifySem: Handles the asynchronous notifications to a BLE Client's notification subscriptions.
•
Command Handler: Interfaces the USB and Bluetooth tasks, interprets commands, and starts the
sensor read task and the scanning tasks.
•
Scan Handler: Controls power to the subsystems necessary to perform a scan (ADS1255, Lamp,
DLPC150), manages the pattern streamed to the DLPC150, and reads sensor information during a
scan. Two semaphores control the start of the scan (scanSem) and the end of a scan (endscanSem).
•
TMP Handler: Manages the temperature readings from the TMP006.
•
HDC Handler: Manages humidity and temperature readings form the HDC1000.
•
microSD Handler: Controls reading and writing data to the microSD card through a FAT32 file system.
A semaphore (sdSem) triggers data access to the microSD card.
DLPU030B – June 2015 – Revised July 2015
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Figure 5-6
shows the typical workflow to compute the reflectance.
client specific.
Absorbance = -log10(Reflectance)
Wavelength
Figure 5-7
Appendix G
Copyright © 2015, Texas Instruments Incorporated
Software System Overview
Absorbance
shows a high-level block diagram of the
.
DLP NIRscan Nano Software
Plot Absorbance
39
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