NXP Semiconductors TWR-S08 User Manual

Contents

NXP Semiconductors TWR-S08 User Manual Manual pdf 13 page image

T W R - S 0 8 L L / L H U S E R G U I D E A P R I L 2 7 , 2 0 1 0U S E R G U I D E13VDD1 EnableThe VDD1 option jumper disconnects the BUZZER, and Light sensor from board power forlow-power operation. Figure 9: below shows the option header settings for use with theVDD1_ENBuzzerThe TWR-S08 board provides an externally modulated piezo-buzzer for audible applications.A push-pull drive circuit allows the target MCU to easily drive the buzzer at a center frequencyof 2400 Hz. Figure 9: below shows the option header settings for use with the buzzer.Light SensorA surface-mount phototransistor, at RZ1, provides light sensitive, variable input for userapplications. Current flow within the phototransistor is inversely proportional to light intensityincident on the surface of the device. A rail-to-rail OP amp at U5 boosts the photocell output touseable levels. Figure 9: below shows the option header settings for use with the light sensorFigure 9: USER1 Option Header, JP7Signal ON OFF  Buzzer PTC2/TPM1CH0 Enabled (*) Disabled  RZ1 PTA6/ADP6 Enabled (*) Disabled  VDD1 VDD Enabled (*) DisabledJP7(*) – Default PositionCAUTION:SW1 and RZ1 share a common MCU signal input. If both components areenabled at the same time, SW 1 may not function properly.Pushbutton SwitchesThe TWR-S08 applies 4, normally open, push-button switches for user input. Each push-button switch is configured for active-low operation. A 22pF capacitor is applied to each push-button switch to minimize switch bounce. An external pull-up is applied to SW4 for use as andIRQ* input; however, no bias is applied to the remaining push-button inputs. Use of targetMCU internal pull-ups is required for proper operation.Figure 10 below shows the user switch connections to the target MCU. Since each push-button switch is normally-open, no option header is applied.