GPIO example

.gitignore

@@ -153,6 +153,8 @@ examples/C/mcmodel/mcmodel_medany
 examples/C/mcmodel/mcmodel_medlow
 examples/C/sum/sum
 examples/C/sum_mixed/sum_mixed
+examples/C/hello/hello
+examples/C/gpio/gpio
 examples/asm/sumtest/sumtest
 examples/asm/example/example
 examples/asm/trap/trap

examples/C/gpio/Makefile

@@ -0,0 +1,33 @@
+TARGET = gpio
+
+$(TARGET).objdump: $(TARGET)
+	riscv64-unknown-elf-objdump -S -D $(TARGET) > $(TARGET).objdump
+	cp $(TARGET) $(TARGET).elf
+    
+$(TARGET): $(TARGET).c Makefile
+	riscv64-unknown-elf-gcc -o $(TARGET) -gdwarf-2 -O\
+	  -march=rv64gc -mabi=lp64d -mcmodel=medany \
+	  -nostdlib -static -lm -fno-tree-loop-distribute-patterns \
+	  -T../common/test.ld -I../common \
+	  $(TARGET).c ../common/crt.S ../common/syscalls.c
+# Compiler flags:
+#  -o $(TARGET) defines the name of the output file
+#  -g generates debugging symbols for gdb
+#  -O turns on basic optimization; -O3 turns on heavy optimization; omit for no optimization
+#  -march=rv64gc -mabi=lp64d =mcmodel=medany generates code for RV64GC with doubles and long/ptrs = 64 bits
+#  -static forces static linking (no dynamic shared libraries on bare metal)
+#  -lm links the math library if necessary (when #include math.h)
+#  -nostdlib avoids inserting standard startup files and default libraries 
+#     because we are using crt.s on bare metal
+#  -fno-tree-loop-distribute-patterns turns replacing loops with memcpy/memset in the std library 
+#  -T specifies the linker file
+#  -I specifies the include path (e.g. for util.h)
+#  The last line defines the C files to compile.  
+#    crt.S is needed as our startup file to initialize the processor
+#    syscalls.c implements printf through the HTIF for Spike
+# other flags from riscv-tests makefiles that don't seem to be important
+#	  -ffast-math -DPREALLOCATE=1 -std=gnu99  \
+#     -fno-common -fno-builtin-printf -nostartfiles -lgcc \
+
+clean:
+	rm -f $(TARGET) $(TARGET).objdump

examples/C/gpio/gpio.c

@@ -0,0 +1,28 @@
+// gpio.c
+// David_Harris@hmc.edu 30 November 2024
+// SPDX-License-Identifier: Apache-2.0 WITH SHL-2.1
+
+// General-Purpose I/O (GPIO) example program illustrating compiled C code
+// compile with make
+// simulate with: wsim rv64gc hello.elf --sim verilator
+
+#include <stdio.h>  
+#include "gpiolib.h"
+
+int main(void) {
+    printf("GPIO Example!\n\r");
+    pinMode(0, INPUT);
+    pinMode(1, OUTPUT);
+    pinMode(2, OUTPUT);
+
+    for (int i=0; i<10; i++) {
+        // Read pin 0 and write it to pin 1
+        int val = digitalRead(0);
+        printf("Pin 0: %d\n", val);
+        digitalWrite(1, val);
+        
+        // Toggle pin 2
+        printf("Pin 2: %d\n", i%2);
+        digitalWrite(2, i%2);
+    }
+}

examples/C/gpio/gpiolib.h

@@ -0,0 +1,81 @@
+// gpiolib.h
+// Basic Arduino-compatible functions for general-purpose input/output
+
+// Assumes GPIO0_BASE is set to the memory-mapped GPIO address from
+// config/rv64gc/config.vh.  
+
+// SPDX-License-Identifier: Apache-2.0 WITH SHL-2.1
+
+#include <stdint.h>
+
+///////////////////////////////////////////////////////////////////////////////
+// Bitfield Structs
+///////////////////////////////////////////////////////////////////////////////
+
+typedef struct
+{
+    volatile uint32_t   input_val;      // (GPIO offset 0x00) Pin value
+    volatile uint32_t   input_en;       // (GPIO offset 0x04) Pin input enable*
+    volatile uint32_t   output_en;      // (GPIO offset 0x08) Pin output enable*
+    volatile uint32_t   output_val;     // (GPIO offset 0x0C) Output value
+    volatile uint32_t   pue;            // (GPIO offset 0x10) Internal pull-up enable*
+    volatile uint32_t   ds;             // (GPIO offset 0x14) Pin drive strength
+    volatile uint32_t   rise_ie;        // (GPIO offset 0x18) Rise interrupt enable
+    volatile uint32_t   rise_ip;        // (GPIO offset 0x1C) Rise interrupt pending
+    volatile uint32_t   fall_ie;        // (GPIO offset 0x20) Fall interrupt enable
+    volatile uint32_t   fall_ip;        // (GPIO offset 0x24) Fall interrupt pending
+    volatile uint32_t   high_ie;        // (GPIO offset 0x28) High interrupt enable
+    volatile uint32_t   high_ip;        // (GPIO offset 0x2C) High interrupt pending
+    volatile uint32_t   low_ie;         // (GPIO offset 0x30) Low interrupt enable
+    volatile uint32_t   low_ip;         // (GPIO offset 0x34) Low interrupt pending
+    volatile uint32_t   iof_en;         // (GPIO offset 0x38) HW-Driven functions enable
+    volatile uint32_t   iof_sel;        // (GPIO offset 0x3C) HW-Driven functions selection
+    volatile uint32_t   out_xor;        // (GPIO offset 0x40) Output XOR (invert)
+    // Registers marked with * are asynchronously reset to 0. All others are synchronously reset to 0.
+} GPIO;
+
+///////////////////////////////////////////////////////////////////////////////
+// GPIO Constant Definitions
+///////////////////////////////////////////////////////////////////////////////
+
+#define GPIO0_BASE  (0x10060000U)   // GPIO memory-mapped base address
+
+#define GPIO0 ((GPIO*) GPIO0_BASE)  // Set up pointer to struct of type GPIO aligned at the base GPIO0 memory-mapped address
+
+#define LOW 0
+#define HIGH 1
+
+#define INPUT 0
+#define OUTPUT 1
+#define GPIO_IOF0 2
+
+///////////////////////////////////////////////////////////////////////////////
+// GPIO Functions
+///////////////////////////////////////////////////////////////////////////////
+
+void pinMode(int pin, int function)
+{
+    switch(function) {
+        case INPUT:
+            GPIO0->input_en     |= (1 << pin);   // Sets a pin as an input
+            break;
+        case OUTPUT:
+            GPIO0->output_en    |= (1 << pin);   // Set pin as an output
+            GPIO0->iof_en       &= ~(1 << pin);
+            break;
+        case GPIO_IOF0:
+            GPIO0->iof_sel      &= ~(1 << pin);
+            GPIO0->iof_en       |= (1 << pin);
+    }
+}
+
+void digitalWrite(int pin, int val)
+{
+    if (val) GPIO0->output_val |= (1 << pin);
+    else     GPIO0->output_val &= ~(1 << pin);
+}
+
+int digitalRead(int pin)
+{
+    return (GPIO0->input_val >> pin) & 0x1;
+}

examples/C/hello/hello.c

@@ -1,5 +1,6 @@
 // hello.c
 // David_Harris@hmc.edu 30 November 2024
+// SPDX-License-Identifier: Apache-2.0 WITH SHL-2.1
 
 // Hello World program illustrating compiled C code printing via the UART
 // The Wally team has modified the Berkeley syscalls.c (in examples/C/common)
@@ -10,7 +11,8 @@
 // such that using \n\r for new lines works best.
 
 // compile with make
-// simulate with: wsim rv64gc hello.elf --sim verilator
+// simulate Wally with: wsim rv64gc hello.elf --sim verilator
+// simulate in Spike with: spike hello.elf
 
 #include <stdio.h>