Enhance GPIO interface

examples/blinky/main.c

 #include <sdk.h>
 
-static int led_pin = 2;
+static int led_pin = LED1;  // To override: make CFLAGS_EXTRA=-DLED1=5
 
 int main(void) {
   wdt_disable();

examples/bme280/Makefile

+SOURCES = main.c
+
+include ../../make/project.mk

examples/bme280/main.c

+#include <sdk.h>
+
+static int led = 2, pin = 4;
+
+int main(void) {
+  wdt_disable();
+  gpio_output(led);
+  gpio_input(pin);
+
+  for (;;) {
+    sdk_log("in: %d\n", gpio_read(pin));
+    gpio_toggle(led);
+    spin(2999999);
+  }
+
+  return 0;
+}

include/gpio.h

-#define GPIO_FUNC_OUT_SEL REG(0X3ff44530)
-#define GPIO_OUT_REG REG(0X3ff44004)
-#define GPIO_ENABLE_REG REG(0X3ff44020)
+#define GPIO_FUNC_OUT_SEL_CFG_REG REG(0X3ff44530)  // Pins 0-39
+#define GPIO_FUNC_IN_SEL_CFG_REG REG(0X3ff44130)   // Pins 0-39
+#define GPIO_OUT_REG REG(0X3ff44004)               // Pins 0-31
+#define GPIO_IN_REG REG(0x3FF4403C)                // Pins 0-31
+#define GPIO_ENABLE_REG REG(0X3ff44020)            // Pins 0-31
+#define GPIO_OUT1_REG REG(0X3ff44010)              // Pins 32-39
+#define GPIO_IN1_REG REG(0X3ff44040)               // Pins 32-39
+#define GPIO_ENABLE1_REG REG(0X3ff4402c)           // Pins 32-39
+
+static inline void gpio_output_enable(int pin, int enable) {
+  volatile unsigned long *r = GPIO_ENABLE_REG;
+  if (pin > 31) pin -= 31, r = GPIO_ENABLE1_REG;
+  r[0] &= ~BIT(pin);
+  r[0] |= (enable ? 1U : 0U) << pin;
+}
 
 static inline void gpio_output(int pin) {
-  GPIO_FUNC_OUT_SEL[pin] = 256;    // Configure GPIO as a simple output
-  GPIO_ENABLE_REG[0] |= BIT(pin);  // Enable pin. See TRM 4.3.3
+  GPIO_FUNC_OUT_SEL_CFG_REG[pin] = 256;  // Simple output, TRM 4.3.3
+  gpio_output_enable(pin, 1);
+}
+
+static inline void gpio_write(int pin, int value) {
+  volatile unsigned long *r = GPIO_OUT_REG;
+  if (pin > 31) pin -= 31, r = GPIO_OUT1_REG;
+  r[0] &= ~BIT(pin);               // Clear first
+  r[0] |= (value ? 1U : 0U) << pin;  // Then set
 }
 
 static inline void gpio_toggle(int pin) {
-  GPIO_OUT_REG[0] ^= BIT(pin);
+  volatile unsigned long *r = GPIO_OUT_REG;
+  if (pin > 31) pin -= 31, r = GPIO_OUT1_REG;
+  r[0] ^= BIT(pin);
+}
+
+static inline void gpio_input(int pin) {
+  // Index lookup table for IO_MUX_GPIOx_REG, TRM 4.12
+  unsigned char map[40] = {17, 34, 16, 33, 18, 27, 24, 25, 26, 21,  // 0-9
+                           22, 23, 13, 14, 12, 15, 19, 20, 28, 29,  // 10-19
+                           30, 31, 32, 35, 36, 9,  10, 11, 0,  0,   // 20-29
+                           0,  0,  7,  8,  5,  6,  1,  2,  3,  4};  // 30-39
+  volatile unsigned long *mux = REG(0X3ff49000);
+  if (pin < 0 || pin > (int) sizeof(map) || map[pin] == 0) return;
+  gpio_output_enable(pin, 0);  // Disable output
+  mux[pin] |= BIT(9);          // Enable input
+}
+
+static inline int gpio_read(int pin) {
+  volatile unsigned long *r = GPIO_IN_REG;
+  if (pin > 31) pin -= 31, r = GPIO_IN1_REG;
+  return r[0] & BIT(pin) ? 1 : 0;
 }

include/sdk.h

@@ -4,6 +4,7 @@
 #pragma once
 
 #include <assert.h>
+#include <errno.h>
 #include <stdarg.h>
 #include <stdlib.h>
 #include <string.h>
@@ -11,7 +12,12 @@
 #define BIT(x) (1UL << (x))
 #define REG(x) ((volatile unsigned long *) (x))
 
+#ifndef LED1
+#define LED1 2  // Default LED pin
+#endif
+
 #include "gpio.h"
+#include "spi.h"
 #include "wdt.h"
 
 static inline void spin(volatile unsigned long count) {

include/spi.h

+struct spi {
+  int miso, mosi, clk, freq;
+};
+
+int spi_init(struct spi *spi);
+int spi_txn(struct spi *spi);

make/project.mk

@@ -6,6 +6,16 @@ PORT      ?= /dev/ttyUSB0
 ESPTOOL   ?= esptool.py
 TOOLCHAIN ?= xtensa-esp32-elf
 
+# -g3 pulls enums and defines into the debug info for GDB
+# -ffunction-sections -fdata-sections, -Wl,--gc-sections remove unused code
+# strict WARNFLAGS protect from stupid mistakes
+
+INCLUDES  ?= -I. -I$(ROOT_PATH)/include
+WARNFLAGS ?= -W -Wall -Wextra -Werror -Wundef -Wshadow -Wdouble-promotion -fno-common -Wconversion
+OPTFLAGS  ?= -Os -g3 -ffunction-sections -fdata-sections
+CFLAGS    ?= $(WARNFLAGS) $(OPTFLAGS) $(MCUFLAGS) $(INCLUDES) $(CFLAGS_EXTRA)
+LINKFLAGS ?= $(MCUFLAGS) -T$(ROOT_PATH)/ld/$(ARCH).ld --gc-sections
+
 ifeq "$(ARCH)" "c3"
 MCUFLAGS  += -march=rv32imc -mabi=ilp32
 WARNFLAGS += -Wformat-truncation
@@ -13,16 +23,6 @@ else
 CFLAGS    += -mlongcalls -mtext-section-literals
 endif
 
-# -g3 pulls enums and defines into the debug info for GDB
-# -ffunction-sections -fdata-sections, -Wl,--gc-sections remove unused code
-# strict WARNFLAGS protect from stupid mistakes
-
-INCLUDES  += -I. -I$(ROOT_PATH)/include
-WARNFLAGS += -W -Wall -Wextra -Werror -Wundef -Wshadow -Wdouble-promotion -fno-common -Wconversion
-OPTFLAGS  += -Os -g3 -ffunction-sections -fdata-sections
-CFLAGS    += $(WARNFLAGS) $(OPTFLAGS) $(MCUFLAGS) $(INCLUDES)
-LINKFLAGS += $(MCUFLAGS) -T$(ROOT_PATH)/ld/$(ARCH).ld --gc-sections
-
 SOURCES += $(wildcard $(ROOT_PATH)/src/*.c)
 OBJECTS = $(SOURCES:%.c=$(OBJ_PATH)/%.o) $(OBJ_PATH)/boot.o
 

src/init.c

@@ -34,8 +34,8 @@ void *sbrk(int diff) {
 }
 
 void __assert_func(const char *a, int b, const char *c, const char *d) {
-  gpio_output(2);
-  for (;;) spin(199999), gpio_toggle(2);
+  gpio_output(LED1);
+  for (;;) spin(199999), gpio_toggle(LED1);
   (void) a;
   (void) b;
   (void) c;

src/spi.c

+// Copyright (c) 2021 Cesanta
+// All rights reserved
+
+#include <sdk.h>
+
+int spi_init(struct spi *spi) {
+  (void) spi;
+  return 0;
+}
+
+int spi_txn(struct spi *spi) {
+  (void) spi;
+  return 0;
+}