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--- pm:prj2025:iivasciuc:marius.zaharia2305 [2025/05/18 13:26]
marius.zaharia2305 [Background and General details]
+++ pm:prj2025:iivasciuc:marius.zaharia2305 [2025/05/25 18:30] (current)
marius.zaharia2305 [Results]
@@ Line 169: / Line 169: @@
 ====Implementation details====
+===Modules===
+**pins**
+  * Contains the mappings between Arduino pins and peripheral components pins.
-===== Results =====
+**sounds**
+  * Contains various sounds for the buzzer, used as audio feedback for the user after certain actions.
+**lights**
+  * Contains multiple color schemes for the RGB LED, used as visual indicators of the menus the user is navigating.
+**wdt_counter**
+  * Controls the Watchdog Timer, by setting it up to generate an interrupt every second.
+  * It is used as a time-keeper for managing the interest gain of the savings accounts (every 15 seconds, interest is applied).
+  * It is preferred instead of Timer0/1/2, because these might be controlled by the ''millis()'' function, which is also used in the project.
+  * If, at a later time, another configuration of the WDT might be preferred (i.e. interrupt after a time interval), only this module is to be modified, without interfering with other sections that use timers.
+  * The source file contains a static variable (private to the file) that represents the counter, offering an init and a getter method for outside modules.
+  * The ISR is rather short and simple, by only incrementing the counter value.
+  * The live value of the counter can be observed in the debug menu.
-===== Conclusions =====
+**debounce**
+  * Offers methods for checking if the joystick is flicked to the right/left/up/down, if the joystick button is pressed and if the red button is pressed.
+  * In the source file, multiple static variables for debounce handling are used, which must not be accessible from the outside.
+  * For button debouncing, a generic function is implemented, which is used by specific functions for the two buttons.
+  * For joystick flicks checking, it is verified if a certain time has passed since the last registered flick, such that there is a delay in the menu navigation system (i.e. the menus do not fall through instantly).
-===== Download =====
+**utils**
+  * Contains utility data structures, constants, global variables marked as ''extern'' and various helper functions.
+  * The ''User'' structure is declared here, containing the necessary information each user must posses.
+  * Functions for keyboard reading, user management, UID card reading and notification handling are specified here.
+**menus**
+  * The enum class that encodes the menus and the functionality of each menu are described here.
+**main**
+  * Initializes the global variables, the user database and all the peripheral devices.
+  * Contains the main loop, which presents the ''switch'' statement by which the current menu function is chosen
-===== Timeline =====
+===How it works===
+  * The users are stored in a statically allocated array, each of them having a predefined name and UID. Initially, all of them are marked as not registered and have to go through the ''register'' menu to become active.
+  * The ''main loop'' is rather simple: at each iteration, it checks the value of the ''curr_menu'' global variable via a ''switch'' and launches the associated routine accordingly. Each such routine then displays its message and enters a ''while(true)'' loop, waiting for user input.
+  * The menus communicate with each other by altering the values of the global variables and of the static variables from the ''menus.cpp'' file.
+  * The goal was to develop a device as realistic and error-less as possible, so extreme cases are always considered, such that: the user is forced to enter a 4-digit PIN code (is not allowed to submit it until it has 4 digits and cannot input more than 4 digits), the user is always allowed to cancel his current action if he changes his mind, hypothetical error states are checked, sending the system to the ''ERROR'' menu if such a case occurs (i.e. if the current menu is the home page of a user, but there is no user logged in).
+  * ''enum class'' have been used for their own namespace feature and for their expressivity compared to numerical constants.
+===Correctness validation===
+  * Each component was firstly tested alone to validate that the hardware was functional.
+  * The system as a whole was incrementally tested, after each new feature added.
+===Optimizations===
+  * Because the maximum number of users is 6, their ''registered'' status was saved as a single 8-bit variable, using bitwise operations: user i is registered if the i-th bit (from the right) of the variable is 1. If each user had a boolean variable associated for this matter, 6 bytes would have been used in total, instead of 1. Thus, 5 bytes are saved.
+  * As the available RAM memory is limited, all the menu message strings were stored on the Flash rather than the RAM, via the ''F()'' macro. Also, variable types from ''<stdint.h>'' were used, for a better control.
+  * The notifications are encoded for memory efficiency: the ''Notification'' struct contains the type (''RecvFromFriend'', ''FriendReq'', ''ReqAccepted''), the index of the user who sent it and the sum of money sent (used when it is the case).
+===== Results =====
+  * The final result is a fully functional, robust device, that encompasses all the proposed features in an intuitive and efficient way, both hardware and software wise.
+  * [[https://youtu.be/4Y1_n8hq_Kc|Demo on YouTube]]
+===== Conclusions =====
+  * To sum up, this project achieved its goal of getting hands-on experience with embedded design, from wiring up the components all the way to writing efficient and functional software.
+  * For me, it was a fun experience with satisfactory results, which I will surely cherish in the future!