Add SoftwareSerial library

.github/workflows/build_examples.yaml

@@ -23,8 +23,8 @@ jobs:
       - name: Generate build matrix
         id: gen_matrix
         run: |
-          # Get all subdirectories containing platformio.ini in the ./example directory
-          subdirectories=$(find ./examples -type f -name "platformio.ini" -exec dirname {} \; | sort -u)
+          # Get all subdirectories containing platformio.ini in the ./examples and ./libraries/*/examples directories
+          subdirectories=$(find ./examples ./libraries/*/examples -type f -name "platformio.ini" -exec dirname {} \; | sort -u)
 
           # Convert subdirectories to JSON array
           json_array="["

cores/arduino/drivers/interrupts/interrupts.cpp

@@ -269,7 +269,7 @@ en_result_t _irqn_aa_resign(IRQn_Type &irqn)
 {
   // do nothing since resigning the interrupt already frees the IRQn
   // only check that the interrupt was actually resigned before calling this function
-  CORE_ASSERT(ram_vector_table.irqs[irqn] != no_handler, "IRQ was not resigned before auto-assign resignment",
+  CORE_ASSERT(ram_vector_table.irqs[irqn] == no_handler, "IRQ was not resigned before auto-assign resignment",
               return Error);
   return Ok;
 }

libraries/SPI/src/SPI.cpp

@@ -3,6 +3,8 @@
 #include <drivers/gpio/gpio.h>
 #include <drivers/sysclock/sysclock.h>
 
+#warning "SPI on the HC32F460 has not been tested yet. See https://github.com/shadow578/framework-arduino-hc32f46x/pull/29" 
+
 /**
  * @brief given a integer v, round up to the next power of two
  * @note based on https://stackoverflow.com/a/466242

libraries/SPI/src/SPI.h

@@ -14,8 +14,6 @@
 #error "SPI library requires PWC DDL to be enabled"
 #endif
 
-#warning "SPI on the HC32F460 has not been tested yet. See https://github.com/shadow578/framework-arduino-hc32f46x/pull/29" 
-
 
 // SPI_HAS_TRANSACTION means SPI has
 //   - beginTransaction()

libraries/SoftwareSerial/README.md

@@ -0,0 +1,92 @@
+# Software Serial for the HC32F460
+
+The Software Serial library allows serial (UART) communication on any digital pin of the board, bit-banging the protocol. 
+It it possible to have multiple software serial ports.
+
+The implementation of this library is based on the [SoftwareSerial library of the STM32duino project](https://github.com/stm32duino/Arduino_Core_STM32/blob/main/libraries/SoftwareSerial/).
+
+
+## Configuration Options
+
+To configure the library, you may add the following defines to your build environment.
+
+| Name | Default | Description |
+|-|-|-|
+| `SOFTWARE_SERIAL_BUFFER_SIZE` | `32` | size of the receive buffer. it's highly likely that any transmission longer than this will be partially lost. |
+| `SOFTWARE_SERIAL_OVERSAMPLE` | `3` | oversampling rate. Each bit period is equal to OVERSAMPLE ticks, and bits are sampled in the middle |
+| `SOFTWARE_SERIAL_HALF_DUPLEX_SWITCH_DELAY` | `5` | bit periods before half duplex switches TX to RX |
+| `SOFTWARE_SERIAL_TIMER_PRESCALER` | `2` | prescaler of the TIMER0. set according to PCLK1 and desired baud rate range |
+| `SOFTWARE_SERIAL_TIMER0_UNIT` | `TIMER01B_config` | TIMER0 unit to use for software serial. Using TIMER01A is not recommended |
+| `SOFTWARE_SERIAL_TIMER_PRIORITY` | `3` | interrupt priority of the timer interrupt |
+| `SOFTWARE_SERIAL_FLUSH_CLEARS_RX_BUFFER` | `SOFTWARE_SERIAL_STM32_API_COMPATIBILITY` | behaviour of the `flush()` method. `0` = waits for pending TX to complete. `1` = clear RX buffer. STMduino library uses behaviour `1` |
+| `SOFTWARE_SERIAL_STM32_API_COMPATIBILITY` | `0` | compatibility with STM32duino library. `0` = sensible API. `1` = compatible with STM32duino API. |
+
+
+> [!TIP]
+> for existing projects that originated from STM32duino, you may set `SOFTWARE_SERIAL_STM32_API_COMPATIBILITY` to `1` to maintain compatibility with the STM32duino library.
+
+
+### Calculating `SOFTWARE_SERIAL_TIMER_PRESCALER`
+
+to calculate, use the following c++ program
+
+```cpp
+#include <iostream>
+#include <stdint.h>
+
+float get_real_frequency(const uint32_t frequency, const uint16_t prescaler)
+{
+    const uint32_t base_frequency = 50000000; // 50 MHz PCLK1
+
+    // calculate the compare value needed to match the target frequency
+    // CMP = (base_freq / prescaler) / frequency
+    uint32_t compare = (base_frequency / uint32_t(prescaler)) / frequency;
+
+    if (compare <= 0 || compare > 0xFFFF)
+    {
+        return -1;
+    }
+
+    // calculate the real frequency
+    float real_frequency = (base_frequency / prescaler) / compare;
+    return real_frequency;
+}
+
+
+int main()
+{
+    const uint32_t baud = 9600;
+    const uint32_t oversampling = 3;
+
+    const uint32_t frequency = baud * oversampling;
+    const uint16_t prescalers[] = {1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024};
+
+    float min_error = 100000;
+    uint16_t best_prescaler = 0;
+    for (auto p : prescalers)
+    {
+        const float real_frequency = get_real_frequency(frequency, p);
+        const float error = std::abs(real_frequency - frequency);
+        if (error < min_error)
+        {
+            min_error = error;
+            best_prescaler = p;
+        }
+
+        std::cout << "Prescaler: " << static_cast<int>(p) 
+                  << ", Real frequency: " << real_frequency 
+                  << ", Error: " << error 
+                  << std::endl;
+    }
+
+    float best_real_frequency = get_real_frequency(frequency, best_prescaler);
+    float best_baud = best_real_frequency / oversampling;
+    float baud_percent_error = (best_baud - baud) / baud * 100;
+    std::cout << "Best prescaler: " << static_cast<int>(best_prescaler) 
+              << ", Real frequency: " << best_real_frequency
+              << ", Error: " << min_error 
+              << ", Real baud rate: " << best_baud
+              << ", Baud rate error: " << baud_percent_error << "%"
+              << std::endl;
+}
+```

libraries/SoftwareSerial/examples/SoftwareSerialExample/.gitignore

@@ -0,0 +1,2 @@
+.pio
+.vscode

libraries/SoftwareSerial/examples/SoftwareSerialExample/platformio.ini

@@ -0,0 +1,17 @@
+[env]
+platform = https://github.com/shadow578/platform-hc32f46x/archive/1.1.0.zip
+framework = arduino
+board = generic_hc32f460
+build_flags =
+    -D USART_AUTO_CLKDIV_OS_CONFIG  # enable auto clock division and oversampling configuration (recommended)
+    -D __DEBUG=1
+    -D __CORE_DEBUG=1
+
+[env:default]
+
+# required only for CI
+[env:ci]
+# override the framework-arduino-hc32f46x package with the local one
+board_build.arduino_package_dir = ../../../../
+extra_scripts = 
+    pre:../../../../tools/ci/patch_get_package_dir.py

libraries/SoftwareSerial/examples/SoftwareSerialExample/src/main.cpp

@@ -0,0 +1,54 @@
+/*
+ * Software serial basic example.
+ *
+ * echos any character received on the software serial port back to the sender.
+ * also allows to change the baud rate by sending a number from 1 to 8.
+ * 
+ * without changing the system clock, the maximum baud rate is around 9600 baud.
+ */
+#include <Arduino.h>
+#include <SoftwareSerial.h>
+
+constexpr gpio_pin_t RX_PIN = PA15;
+constexpr gpio_pin_t TX_PIN = PA9;
+
+SoftwareSerial mySerial(/* RX */ RX_PIN, /* TX */ TX_PIN);
+
+void setup() 
+{
+  mySerial.begin(9600);
+  mySerial.println("Hello, world!");
+}
+
+void loop() 
+{
+  while (mySerial.available())
+  {
+    const char c = mySerial.read();
+    mySerial.write(c);
+
+    uint32_t new_baud = 0;
+    switch(c)
+    {
+      case '1': new_baud = 1200; break;
+      case '2': new_baud = 2400; break;
+      case '3': new_baud = 4800; break;
+      case '4': new_baud = 9600; break;
+      case '5': new_baud = 19200; break;
+      case '6': new_baud = 38400; break;
+      case '7': new_baud = 57600; break;
+      case '8': new_baud = 115200; break;
+      default: break;
+    }
+    if (new_baud != 0)
+    {
+      mySerial.print("Set baud to:");
+      mySerial.print(new_baud);
+      delay(100);
+      mySerial.begin(new_baud);
+      mySerial.println(" - Done");
+    }
+  }
+
+  delay(10);
+}