UPC EETAC Bachelor's Degree in Telecommunications Systems and in Network Engineering EEL
 

 

1-digit BCD counter with LCD and TMR1 and A/D (design phase #4)

P12

A/D example application

1. Specifications Planning Dev. & test Prototype  report

A way to introduce analogue to digital conversions, is to use an external potentiometer. The analogue input signal vA from the potentiometer AN0 available on the CSD_PICstick board is captured by the PIC18F46K22 10-bit analogue to digital (A/D) converter.

Analogue to digital conversion

Fig. 1. Analogue to digital conversion.

We can use the previous phase #3 timing periods TP = 1 s or TP = 8.33 ms as sampling periods TS. The push-button Sel_freq will select between fS = 1 Hz and fS = 12 Hz.

This time let us use the CSD_PICstick switch CE to select between representing analogue voltages or counting BCD values.

Symbol adding the analogue to digital conversion

Fig. 2. Symbol and signals used in this design phase #4.

 

Specifications 2. Planning Dev. & test Prototype  report

A) Planning hardware

The only new connection from the previous design phase #3 is the AN0 analogue input at pin RA0.

B) Planning software

We need to synchronise analogue to digital conversion on TMR1 interrupts as the way to fix the sampling frequency at the same var_CLK_flag. In this simple application, most of the A/D parameters will be fixed in init_system(). The function analogue_read() will start conversions and wait for end of conversion in a few microseconds (conversion time TC = 11·TAD). 

Example of software-hardware diagram

Fig. 3. Hardware-software diagram.

Organise an MPLABX - XC8 IDE project targeting a PIC18F46K22 at location:

C:\CSD\P12\c_BCD_1d_LCD_TMR1_AD\(files)

 

Specifications Planning 3. Dev. & 4. test Prototype  report

A) Developing hardware

This is the circuit in Proteus: "Counter_BCD_1digit_LCD_TMR1_AD.pdsprj".

microcntroller pinning

Fig. 4. µC connections.

 

B) Developing software

The XC8 compiler version is v3.0 or newer, C standard is C99. And these LCD library files "lcd.c", "lcd.h" have to be included in the project. The file "config.h" contains all the microcontroller configuration bits.

This is the source file: "Counter_BCD_1digit_LCD_TMR1_AD.c".

C) Step-by-step testing

A/D converter running

Fig. 4. Counter_BCD_1digit_LCD_TMR1_AD captured in Proteus showing RAM variable is the watch window and all the mC pins in use.

 

Specifications Planning Dev. & Test 5. Prototype  Report

We have adapted the hardware so that we can mount the application using the PCD_PICstick.

 

Specifications Planning Dev. & Test Prototype 6. Report

Follow this rubric for writing reports.