CY8CKIT-006 Cypress Semiconductor Corp, CY8CKIT-006 Datasheet - Page 27

• Manufacturer Part Number: CY8CKIT-006
• Description: KIT DEV PSOC3 LCD SEGMENT
• Manufacturer: Cypress Semiconductor Corp
• Series: PSOC™ 3r

Specifications of CY8CKIT-006

• Main Purpose: Displays, LCD Display
• Embedded: Yes, MCU, 32-Bit
• Primary Attributes: 448 addressable segments
• Secondary Attributes: Configurable LCD pin selection
• Description/function: Evaluation Kit
• Interface Type: USB
• Backlighting: No Backlighting
• Data Bus Width: 8 bit, 16 bit, 32 bit
• Maximum Operating Temperature: + 50 C
• Minimum Operating Temperature: 0 C
• Number Of Segments: 7
• Operating Supply Voltage: 12 V
• Operating Voltage: 3.3 V
• Pixel Format: 16 x 28
• Product: Display Modules
• Software: Software Included
• Touch Panel: No Touch Panel
• For Use With/related Products: PSoC 3
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Utilized Ic / Part: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 428-2994

5.2.2.1
5.2.3
CY8CKIT-006 PSoC 3 LCD Segment Drive Evaluation Kit Guide, Doc. # 001-52798 Rev. *C
Temperature Sensing Design Principle
The device for temperature sensing uses a voltage divider with a precision resistor on one side and
the thermistor on the other to estimate the thermistor resistance. This is shown in
temperature calculations are as accurate as the resistance measurement of the thermistor.
Figure 5-3. Temperature Sensing Design
This setup significantly removes gain and offset errors from the resistance calculation.
The analog voltage output from the divider is converted to a digital signal using the ADC on the
PSoC. To gain additional accuracy, the voltage at the input side of the divider is also measured. The
resistor value is calculated using the ratio of the voltages across the two resistors in the resistor lad-
der.
Rthermistor = Rref * (V0-V1/V1-V2); where V2 = 0 (Ground voltage)
Any offset errors are removed due to subtraction of the two measured voltages. The ratio of these
two values removes the measurement path gain error. The error due to the reference resistor is
reduced by using a precision resistance in series with the thermistor.
Temperature is calculated using a table of 165 known points on the resistance/temperature curve
using a look up table. The table holds resistance values of the thermistor from -40°C to 125°C, in 1°C
increments. Linear interpolation is used between the points in the table for temperature calculation
up to two places after the decimal.
Temperature is also calculated using the Steinhart-Hart equation. This project currently feeds in the
Steinhart-Hart calculated temperature for display.
For more information on using PSoC family devices with a thermistor, refer to Cypress Application
Note, AN2017, Sensing - A Thermistor-Based Thermometer, PSoC Style.
RTC Crystal and Clocking
The RTC maintains a high precision based on the application of an accurate crystal input used as
the clock source. The RTC component inserted by the PSoC Creator provides API calls that can be
used to set the time and date and to read the instantaneous current time and date. When the device
is in the Show Time sub mode, the code simply loops on CapSense button scans and reads and dis-
plays the instantaneous time and date information. The temperature at the board thermistor is sam-
Figure
5-3. The
Firmware
27
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