K E Y B O A R D S (3).

Transcription

1 Course on BASCOM AVR - (12) Theoretic/Practical course on BASCOM AVR Programming. Author: DAMINO Salvatore. K E Y B O A R D S (3). This program describes with details a complete solution of all the problems concerning the management of a Matrix Keyboard. Keyboard 4x4 Electric Diagram. 72

2 The examined concepts show either how to acquire the keyboard with required securities of Debouncing (described in previous chapters), and the Autorepeat operations, when a key is continuosly pressed. By changing the timings defined in the program it is possible to change the operative modalities and so the user can adapt the keyboard functionality to different applications requirements. The Flow chart at the end of chapter has been realized in order to explain the program parts and their relationship. It is composed by a general structure and some explosions of the most important components parts. In addition to flow chart it is important to read the numerous remarks available in the program source. In fact, they show in details the used variables and constants and explain some strattagemmi used for autorepeat implementation. 73

3 Example.019. Keyboard management. Debouncing and Autorepeat modality. Added Definitions: ne Added Declarations: ne Added Instructions: ne Added Operators: ne Example Program.019 of BASCOM AVR course. It manages all keys of a 4x4 matrix keyboard. The program continuosly acquires the state of the 16 keys connected to matrix keyboard available on GMM TST3 and i t transmits them on serial line. The acquisition is performed with Debouncing and Autorepeat: the keys are acquired with a Debouncing time of 20 milliseconds, the first key with Autorepeat is supplied after 500 milliseconds and the following ones after 100 milliseconds. The visualization of pressed keys is performed on a serial console provided of monitor and it must communicate with a fixed physical protocol at Baud, 8 Bit x chr, 1 Stop bit, parity. This console can be another system capable to support a serial RS communication. In order to simplify the use it can be used a PC provided of one COMx line, that execute a terminal emulation program as HYPERTERMINAL or the homonym modality provided by BASCOM AVR (see IDE Configuration). The program works only when the GMM AM08 is mounted on Z1 socket of GMM TST3!! Inside the program the Row and Column terms refer to electric diagram of matrix keyboard, not to its physical format!! 74

4 Start Initialize signals for serial communication as digital inputs 1: Initialize lines and variables for matrix keyboard management Show program user instructions on serial console Begin Endless Loop Perform a delay equal to Debouncing time 2: Acquire matrix keyboard state with Debouncing and Autorepeat Is real key pressed? Show real key pressed on console End Endless Loop Flow Chart Diagram of the Program. 75

5 Set signals for matrix keyboard as digital I/O Initialize signals connected to rows of matrix keyboard as digital inputs Initialize signals connected to columns of matrix keyboard as digital outputs, high Set codes of matrix keyboard keys in proper array with index equal to key position Initialize variables: no key under Debouncing and reset Debouncing counter Initialize variables: no key under Autorepeat and reset Autorepeat counter 1: Initialize Lines and Variables for Matrix Keyboard Management. Initialize code of real key pressed for no key 2.1: Acquire matrix keyboard state with Debouncing Key pressed during acquisition Set no key under Autorepeat Reset Autorepeat counter Key already pressed, that is under Autorepeat Save position of new key under Autorepeat Reset Autorepeat counter Get code of real key pressed from proper array, with index = key position Increase Autorepeat counter Autorepeat time elapsed, that is Autorepeat counter >= maximum predefined time Set counter for next Autorepeat Get code of real key pressed from proper array, with index = key position 2: Acquire Matrix keyboard State with Debouncing and Autorepeat. 76

6 Initialize position of real key pressed for no key 2.1.1: Perform matrix keyboard scanning and obtain possible key pressed position Key pressed during scanning Set no key under Debouncing Reset Debouncing counter Key already pressed, that is under Debouncing Save position of new key under Debouncing Reset Debouncing counter Increase Debouncing counter Debouncing time elapsed, that is Debouncing counter >= predefined time Return real key pressed position Reset Debouncing counter 2.1: Acquire matrix keyboard state with Debouncing. 77

7 Initialize key pressed position for no key Initialize current column of matrix keyboard on first one Start Loop : Set low current column of matrix keyboard : Acquire rows states of matrix keyboard Key pressed on current column (at least one row is low) Obtain position of key pressed from column and row, starting from 0, or it multiply column by 4 and adds row Incrase key pressed position (starting from 1), in order to obtain corrispondence with indexes of key codes array Increase current column of matrix keyboard End loop repeated for the 4 columns of the matrix keyboard (current column > 3) 2.1.1: Perform Matrix Keyboard Scanning and obtain Possible Key Pressed Position. 78

8 Current column = 0 (first) Set high the line connected to first column of matrix keyboard Set low the line connected to first column of matrix keyboard Current column = 1 (second) Set high the line connected to second column of matrix keyboard Set low the line connected to second column of matrix keyboard Current column = 2 (third) Set high the line connected to third column of matrix keyboard Set low the line connected to third column of matrix keyboard Current column = 3 (fourth) Set high the line connected to fourth column of matrix keyboard Set low the line connected to fourth column of matrix keyboard : Set Low Current Column of Matrix Keyboard. Initialize rows states of matrix keyboard for no key pressed Lines connected to first row is low Lines connected to second row is low Lines connected to third row is low Lines connected to fourth row is low Set rows states of keyboard = 0 (key pressed on first row) Set rows states of keyboard = 1 (key pressed on second row) Set rows states of keyboard = 2 (key pressed on third row) Set rows states of keyboard = 3 (key pressed on fourth row) : Acquire Rows State of Matrix Keyboard. 79