Cypress CapSense CY8C20x36 Guía de usuario descargar pdf (Pagina 27)

Getting Started with CapSense

Document No. 001-64846 Rev. *I 27

The linear brightness levels are transferred to exponential duty cycle values using the lookup table. The following

expression is used for the conversion:





 















 



Equation 9

 



















Equation 10

Figure 2-26 illustrates the table graphs at different values of parameter b. Note that N

MAX

is set to 255. This

expression converts an 8-bit unsigned byte value to the same range. The figure shows that the transfer characteristic

becomes more exponential as the b parameter increases.

Figure 2-26. LED Duty Cycle Conversion Table

0 50 100 150 200 250

100

150

200

250

LED Lookup table

out

b =0.005

b =0.014

b =0.023

b =0.032

b =0.041

2.7.1.2 LCD-based Visual Feedback

LCDs provide visual feedback for CapSense buttons and sliders. The main advantage of using an LCD is that it can

provide more information along with the feedback for each button press event. PSoC has built-in user modules for

driving Hitachi HD44780A LCD module. This user module supports high-level and low-level APIs that can directly

display data on the screen with ease. Figure 2-27 shows the typical connection for using the Hitachi HD44780A LCD

module.

Figure 2-27. Hitachi Dot Matrix LCD Pin Connections

PSoC can also control LCDs through I

C. The I2CHW user module available in PSoC controls the GLK 24064-25 WB

graphics LCD. Sending the commands through the I

C bus is simplified. The CSD user module is configured to scan

a set of buttons and any button press event initiates an I

C transfer from the PSoC to the LCD as a feedback.

The typical circuit diagram for driving the GLK 24064-25 WB graphics LCD follows.

1 2 ... 22 23 24 25 26 27 28 29 30 31 32 ... 74 75

Comentarios a estos manuales

Sin comentarios

Cypress CapSense CY8C20x36 Guía de usuario Pagina 27

Comentarios a estos manuales