[sw] add twd demo

sw/example/demo_twd/main.c

@@ -0,0 +1,98 @@
+// ================================================================================ //
+// The NEORV32 RISC-V Processor - https://github.com/stnolting/neorv32              //
+// Copyright (c) NEORV32 contributors.                                              //
+// Copyright (c) 2020 - 2025 Stephan Nolting. All rights reserved.                  //
+// Licensed under the BSD-3-Clause license, see LICENSE for details.                //
+// SPDX-License-Identifier: BSD-3-Clause                                            //
+// ================================================================================ //
+
+
+/**********************************************************************//**
+ * @file demo_twd/main.c
+ * @author Lukas Pajak
+ * @brief TWD demo.
+ **************************************************************************/
+
+#include <neorv32.h>
+#include <string.h>
+
+
+/**********************************************************************//**
+ * @name User configuration
+ **************************************************************************/
+/**@{*/
+/** UART BAUD rate */
+#define BAUD_RATE 19200
+/** TWD id */
+#define TWD_DEVICE_ID 0x3f
+/**@}*/
+
+
+// Prototypes
+void isr_twd(void);
+
+
+/**********************************************************************//**
+ * This program provides a simple demo as TWD device.
+ * A connected TWI Host is required.
+ *
+ * @note This program requires the UART to be synthesized.
+ *
+ **************************************************************************/
+int main() {
+  // capture all exceptions and give debug info via UART
+  // also handles isr for TD
+  neorv32_rte_setup();
+
+  // check if UART unit is implemented at all
+  if (neorv32_uart0_available() == 0) {
+    return 1;
+  }
+
+  // setup UART at default baud rate, no interrupts
+  neorv32_uart0_setup(BAUD_RATE, 0);
+  neorv32_uart0_printf("\n\n<< TWD status demo >>\n");
+  neorv32_uart0_printf(__DATE__ "\n");
+  neorv32_uart0_printf(__TIME__ "\n");
+
+  uint8_t status = 0x03;
+
+  // check for TWD
+  if (!neorv32_twd_available()) {
+    neorv32_uart0_printf("TWD not available\n");
+    return 1;
+  } else {
+    neorv32_uart0_printf("TWD available with rx fifo depth of %i and tx fifo depth of %i\n",
+                         neorv32_twd_get_rx_fifo_depth(), neorv32_twd_get_tx_fifo_depth());
+  }
+  
+  // setup TWD
+  neorv32_rte_handler_install(TWD_RTE_ID, isr_twd);
+  neorv32_twd_set_dummy(status);
+  neorv32_twd_setup(TWD_DEVICE_ID, 0, 1, 0, 0, 1);
+  neorv32_cpu_csr_set(CSR_MIE,
+                      1 << TWD_FIRQ_ENABLE); 
+  neorv32_cpu_csr_set(CSR_MSTATUS,
+                      1 << CSR_MSTATUS_MIE);
+
+  // Fill TX Fifo
+  for (uint8_t i = 0; i < neorv32_twd_get_tx_fifo_depth(); i++)
+  {
+    neorv32_twd_put(i);
+  }
+
+  neorv32_uart0_printf("Listen now on %x\n", TWD_DEVICE_ID);
+  neorv32_uart0_printf("Read should return %i data byte(s) once and %x when TX FIFO is empty.\n", neorv32_twd_get_tx_fifo_depth(), status);
+  while (1) {}
+}
+
+/***
+ * ISR of TWD for read access
+*/
+void isr_twd(void) {
+  uint8_t data = neorv32_twd_get();
+  neorv32_uart0_printf("Got %x\n", data);
+  neorv32_twd_disable_dummy();
+  neorv32_uart0_printf("Read should fail (or return 0xFF when in the same transaction) when TX FIFO is empty.\n");
+  neorv32_twd_put(data);
+}

sw/example/demo_twd/makefile

@@ -0,0 +1,33 @@
+# Application makefile.
+# Use this makefile to configure all relevant CPU / compiler options.
+
+# Override the default CPU ISA
+MARCH = rv32i_zicsr_zifencei
+
+# Override the default RISC-V GCC prefix
+#RISCV_PREFIX ?= riscv-none-elf-
+
+# Override default optimization goal
+EFFORT = -Os
+
+# Add extended debug symbols
+USER_FLAGS += -ggdb -gdwarf-3
+
+# Adjust processor IMEM size
+USER_FLAGS += -Wl,--defsym,__neorv32_rom_size=16k
+
+# Adjust processor DMEM size
+USER_FLAGS += -Wl,--defsym,__neorv32_ram_size=8k
+
+# Adjust maximum heap size
+#USER_FLAGS += -Wl,--defsym,__neorv32_heap_size=1k
+
+# Additional sources
+#APP_SRC += $(wildcard ./*.c)
+#APP_INC += -I .
+
+# Set path to NEORV32 root directory
+NEORV32_HOME ?= ../../..
+
+# Include the main NEORV32 makefile
+include $(NEORV32_HOME)/sw/common/common.mk