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Initial published version.
Diff: main.cpp
- Revision:
- 109:744c6cb711bf
- Parent:
- 108:eee3167b25b4
- Child:
- 110:8170476d91a6
diff -r eee3167b25b4 -r 744c6cb711bf main.cpp --- a/main.cpp Tue Sep 21 02:00:55 2021 +0000 +++ b/main.cpp Thu Sep 23 03:03:59 2021 +0000 @@ -1,31 +1,67 @@ /* - Project: BinaryCount + Project: Button Tests File: main.cpp - Displays 8 bit binary count on bar graph display. + This program demonstrates User Button behavior. Written by: Dr. C. S. Tritt - Created: 9/20/21 (v. 1.2) + Created: 9/22/21 (v. 1.0) */ #include "mbed.h" -BusOut barGraph(D2, D3, D4, D5, D6, D7, D8, D9); // Create BusOut object. +DigitalIn uB(USER_BUTTON); // Active low! Normally 1 go to 0 when pressed. int main() { - // Test the wiring. - barGraph = 0; // All bars off (base 10). - ThisThread::sleep_for(400); // For 0.4 seconds. - barGraph = 0b01010101; // Odd bars on (binary). - ThisThread::sleep_for(400); // Test even bars for 0.4 seconds. - barGraph = 0b10101010; // Even bars on (binary). - ThisThread::sleep_for(400); // Test even bars for 0.4 seconds. - barGraph = 0xFF; // All bars on. Hex. - ThisThread::sleep_for(400); // For 0.4 seconds. - // Enter main loop. + // Enter main loop. Sequential calls to the button like this is generally + // not good practice, but I want to use the DigitalIn object in these + // contexts to illustrate my points. See while loop below for a better + // (more common and realistic) approach. while(true) { - for (int i = 0; i < 256; i++) { // Add one to count. - barGraph = i; // Copy the count to the bargraph. - ThisThread::sleep_for(100); // Display the value for 0.1 seconds. - } - } -} \ No newline at end of file + // Use the button in some printf calls. + printf("\nuB (w/o cast) = %d.\n", uB); // Bad! Warning! Wrong! + printf("uB (with int cast) = %d.\n", static_cast<int>(uB)); + // I found a reference that claimed there is a %b (or B) speicifer for + // type bool, but it doesn't work in mbed. + printf("uB (with bool cast) = %d.\n", static_cast<bool>(uB)); + printf("uB.read = %d.\n", uB.read()); + + // Use the button in some if constructs. No need to compare. No need to + // use .read(). + if (uB) + printf("In if (uB).\n"); + if (uB.read()) + printf("In if (uB.read()).\n"); + if (!uB) + printf("In if (!uB).\n"); + if (!uB.read()) + printf("In if (!uB.read()).\n"); + ThisThread::sleep_for(500); // For 0.5 seconds after some output. + + // Best practice is to get and save the button state and use until you + // are done with your response to it. + int count = 5; // Count for loop below. + bool uBstate = uB; // Get the buttons state. Save it and use it. + // uB could change states between the if below and the following while. + // This would result in an extra line of output without the contents of + // the while being output. That is what the use of uBstate prevents. + if (!uBstate) printf("\n"); // Print extra line before while output. + while (!uBstate && count >= 1) { + // Count down from 5 to 1. + // Do something here with uBstate false & assuming uB is false. + // Decrement after use! + printf("In while loop. Count = % d.\n", count--); + // Now determine if state has changed. + if (uB != uBstate) { + printf("The button changed while in the loop. Exiting.\n"); + // Using a while and setting exit conditions is generally better + // than using a break. Strive for one way in and one way out in + // all your code for more reliability and easier maintenance. + // But there are exceptions to this rule. That is why break (and + // continue exist. + uBstate = !uBstate; // Update uBstate to exit loop. + } //end of if. + ThisThread::sleep_for(500); // For 0.5 seconds in while. + } // end of !uBstate while. + printf("End of main while.\n\n"); + } // end of main while. +} // end of main function. \ No newline at end of file