Up Down Counter using FSM

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API Documentation at this revision

Comitter:
eencae
Date:
Thu Dec 10 13:42:11 2020 +0000
Commit message:
Initial Commit

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+.build
+.mbed
+projectfiles
+*.py*
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+# Contributing to Mbed OS
+
+Mbed OS is an open-source, device software platform for the Internet of Things. Contributions are an important part of the platform, and our goal is to make it as simple as possible to become a contributor.
+
+To encourage productive collaboration, as well as robust, consistent and maintainable code, we have a set of guidelines for [contributing to Mbed OS](https://os.mbed.com/docs/mbed-os/latest/contributing/index.html).
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+![](./resources/official_armmbed_example_badge.png)
+# Blinky Mbed OS example
+
+The example project is part of the [Arm Mbed OS Official Examples](https://os.mbed.com/code/) and is the [getting started example for Mbed OS](https://os.mbed.com/docs/mbed-os/v5.14/quick-start/index.html). It contains an application that repeatedly blinks an LED on supported [Mbed boards](https://os.mbed.com/platforms/).
+
+You can build the project with all supported [Mbed OS build tools](https://os.mbed.com/docs/mbed-os/latest/tools/index.html). However, this example project specifically refers to the command-line interface tool [Arm Mbed CLI](https://github.com/ARMmbed/mbed-cli#installing-mbed-cli).
+(Note: To see a rendered example you can import into the Arm Online Compiler, please see our [import quick start](https://os.mbed.com/docs/mbed-os/latest/quick-start/online-with-the-online-compiler.html#importing-the-code).)
+
+1. [Install Mbed CLI](https://os.mbed.com/docs/mbed-os/latest/quick-start/offline-with-mbed-cli.html).
+
+1. Clone this repository on your system, and change the current directory to where the project was cloned:
+
+    ```bash
+    $ git clone git@github.com:armmbed/mbed-os-example-blinky && cd mbed-os-example-blinky
+    ```
+
+    Alternatively, you can download the example project with Arm Mbed CLI using the `import` subcommand:
+
+    ```bash
+    $ mbed import mbed-os-example-blinky && cd mbed-os-example-blinky
+    ```
+
+
+## Application functionality
+
+The `main()` function is the single thread in the application. It toggles the state of a digital output connected to an LED on the board.
+
+## Building and running
+
+1. Connect a USB cable between the USB port on the board and the host computer.
+2. <a name="build_cmd"></a> Run the following command to build the example project and program the microcontroller flash memory:
+    ```bash
+    $ mbed compile -m <TARGET> -t <TOOLCHAIN> --flash
+    ```
+The binary is located at `./BUILD/<TARGET>/<TOOLCHAIN>/mbed-os-example-blinky.bin`.
+
+Alternatively, you can manually copy the binary to the board, which you mount on the host computer over USB.
+
+Depending on the target, you can build the example project with the `GCC_ARM`, `ARM` or `IAR` toolchain. After installing Arm Mbed CLI, run the command below to determine which toolchain supports your target:
+
+```bash
+$ mbed compile -S
+```
+
+## Expected output
+The LED on your target turns on and off every 500 milliseconds.
+
+
+## Troubleshooting
+If you have problems, you can review the [documentation](https://os.mbed.com/docs/latest/tutorials/debugging.html) for suggestions on what could be wrong and how to fix it.
+
+## Related Links
+
+* [Mbed OS Stats API](https://os.mbed.com/docs/latest/apis/mbed-statistics.html).
+* [Mbed OS Configuration](https://os.mbed.com/docs/latest/reference/configuration.html).
+* [Mbed OS Serial Communication](https://os.mbed.com/docs/latest/tutorials/serial-communication.html).
+* [Mbed OS bare metal](https://os.mbed.com/docs/mbed-os/latest/reference/mbed-os-bare-metal.html).
+* [Mbed boards](https://os.mbed.com/platforms/).
+
+### License and contributions
+
+The software is provided under Apache-2.0 license. Contributions to this project are accepted under the same license. Please see contributing.md for more info.
+
+This project contains code from other projects. The original license text is included in those source files. They must comply with our license guide.
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+/*
+
+2645_FSM_UpDown_Counter
+
+Sample code from ELEC2645
+
+Demonstrates how to implement a simple FSM up/down counter
+
+(c) Craig A. Evans, University of Leeds, Jan 2016
+Updated Jan 2020
+Updated Dec 2020
+
+*/
+
+#include "mbed.h"
+#include "platform/mbed_thread.h"
+
+// defines directions as 0/1. Note UPPERCASE
+#define UP 0
+#define DOWN 1
+
+// create a bus for writing to the output (LEDs) at once
+BusOut output(LED4,LED3,LED2,LED1);
+// Button A on board
+InterruptIn buttonA(p29);
+
+// array of states in the FSM, each element is the output of the counter
+// set the output in binary to make it easier, 1 is LED on, 0 is LED off
+int g_fsm[4] = {0b0001,0b0010,0b0100,0b1000};
+
+// flag - must be volatile as changes within ISR
+// g_ prefix makes it easier to distinguish it as global
+volatile int g_buttonA_flag = 0;
+
+// Button A interrupt service routine
+void buttonA_isr();
+
+int main()
+{
+    // Button A has a pull-down resistor, so the pin will be at 0 V by default
+    // and rise to 3.3 V when pressed. We therefore need to look for a rising edge
+    // on the pin to fire the interrupt
+    buttonA.rise(&buttonA_isr);
+    // since Button A has an external pull-down, we should disable to internal pull-down
+    // resistor that is enabled by default using InterruptIn
+    buttonA.mode(PullNone);
+  
+    // set inital state
+    int state = 0;
+    // set initial direction
+    int direction = UP;
+
+    while(1) {  // loop forever
+
+        // check if flag i.e. interrupt has occured
+        if (g_buttonA_flag) {
+            g_buttonA_flag = 0;  // if it has, clear the flag
+
+            // swap direction when button has been pressed
+            // (could just use ! but want this to be explicit to aid understanding)
+            if (direction == UP) {
+                direction = DOWN;
+            } else {
+                direction = UP;
+            }
+        }
+
+        output = g_fsm[state];  // output current state
+
+        // check which state we are in and see which the next state should be next depending on direction
+        switch(state) {
+            case 0:
+                switch(direction) {
+                    case UP:
+                        state = 1;
+                        break;
+                    case DOWN:
+                        state = 3;
+                        break;
+                }
+                break;
+            case 1:
+                switch(direction) {
+                    case UP:
+                        state = 2;
+                        break;
+                    case DOWN:
+                        state = 0;
+                        break;
+                }
+                break;
+            case 2:
+                switch(direction) {
+                    case UP:
+                        state = 3;
+                        break;
+                    case DOWN:
+                        state = 1;
+                        break;
+                }
+                break;
+            case 3:
+                switch(direction) {
+                    case UP:
+                        state = 0;
+                        break;
+                    case DOWN:
+                        state = 2;
+                        break;
+                }
+                break;
+            default:  // default case
+                error("Invalid state!");  //invalid state - call error routine
+                state = 0;
+                break;
+        }
+
+        thread_sleep_for(500);
+    }
+}
+
+// Button A event-triggered interrupt
+void buttonA_isr()
+{
+    g_buttonA_flag = 1;   // set flag in ISR
+}
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+https://github.com/ARMmbed/mbed-os/#cf4f12a123c05fcae83fc56d76442015cb8a39e9
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