User manual

MCP355X Sensor Application Developer’s Board User’s Guide

3.2.2.5 FULL-SCALE VALUE SELECTION

This menu options loads the DISPLAY_FS_VAL register. This is to allow for proper LCD

display during system design. For example, if a system is being designed that uses

“100 grams” as the full-scale calibration weight, this menu is used to set the value “100”

into the DISPLAY_FS_VAL register. The full-scale value options are 1, 2, 5, 10, 20, 50,

100, 200, or 500.

3.2.2.6 FULL-SCALE CALIBRATION

When in this menu, the second button becomes the calibrate full-scale button, labeled

OK. When this button is selected, the most recent ADC value, after averaging, will be

loaded into the FS

CAL

3.3 PIC18F4550

This device acts as I

C slave and passes the PIC16F877 output data from either

channel 1 or channel 2 to the DataView on the PC. All averaging and channel 1

switching that is performed by the PIC16F877 occurs before the data is passed to the

PIC18F4550 and PC.

Note: If the channel mode “Channel 1 Switching” is selected, the averaging will

actually be twice due to the positive and reverse polarity switched samples

being collected.

Note: When displaying the value on the LCD display, the decimal point does not

move. This is to relax the LCD activity and keep the decimal point (and all

digits) from constantly switching location when the LCD output is

calculated.

Note: The PIC18F4550 passes data to DataView on the PC coming from the

PIC16F877. This allows a system developer to write PIC16F877 firmware

that averages or otherwise post processes ADC data and then use the PC

to view this post processed data, see section below. Refer to Figure 2-1 for

Data Flow.