cpu/sam0_common: implement periph_gpio_read_output

cpu/sam0_common/periph/gpio.c

@@ -163,26 +163,33 @@
     int pin_mask = _pin_mask(pin);
 
     /* make sure pin mode is applicable */
-    if (mode > 0x7) {
+    if (mode & ~MODE_PINCFG_MASK) {
         return -1;
     }
 
     /* set pin direction */
-    if (mode & 0x2) {
+    if (mode & PORT_PINCFG_INEN) {
+        /* input */
         if (IS_ACTIVE(MODULE_PERIPH_GPIO_FAST_READ)) {
             port->CTRL.reg |= pin_mask;
         }
         port->DIRCLR.reg = pin_mask;
     }
     else {
+        /* output */
         if (IS_ACTIVE(MODULE_PERIPH_GPIO_FAST_READ)) {
             port->CTRL.reg &= ~pin_mask;
         }
         port->DIRSET.reg = pin_mask;
+
+        /* enable input to read back output level */
+        if (IS_ACTIVE(MODULE_PERIPH_GPIO_READ_OUTPUT)) {
+            mode |= PORT_PINCFG_INEN;
+        }
     }
 
     /* configure the pin cfg */
-    port->PINCFG[pin_pos].reg = (mode & MODE_PINCFG_MASK);
+    port->PINCFG[pin_pos].reg = mode;
 
     /* and set pull-up/pull-down if applicable */
     if (mode == GPIO_IN_PU) {
@@ -207,11 +214,11 @@
         port = _port(pin);
     }
 
-    if (port->DIR.reg & mask) {
-        return (port->OUT.reg & mask) ? 1 : 0;
-    }
-    else {
-        return (port->IN.reg & mask) ? 1 : 0;
+    if (IS_ACTIVE(MODULE_PERIPH_GPIO_READ_OUTPUT) ||
+        !(port->DIR.reg & mask)) {
+        return port->IN.reg & mask;
+    } else {
+        return port->OUT.reg & mask;
     }
 }
 
@@ -244,10 +251,10 @@
 #ifdef CPU_COMMON_SAMD21
 #define EIC_SYNC() while (_EIC->STATUS.reg & EIC_STATUS_SYNCBUSY)
 #else
 #define EIC_SYNC() while (_EIC->SYNCBUSY.reg & EIC_SYNCBUSY_ENABLE)
 #endif
 
 static int _exti(gpio_t pin)
 {
     unsigned port_num = ((pin >> 7) & 0x03);
 

cpu/samd21/Makefile.features

@@ -1,6 +1,7 @@
 CPU_CORE = cortex-m0plus
 
 FEATURES_PROVIDED += periph_gpio_fast_read
+FEATURES_PROVIDED += periph_gpio_read_output
 
 ifeq (,$(filter samd20%,$(CPU_MODEL)))
   FEATURES_PROVIDED += periph_uart_collision

cpu/samd5x/Makefile.features

@@ -3,6 +3,7 @@ CPU_CORE = cortex-m4f
 FEATURES_PROVIDED += periph_hwrng
 FEATURES_PROVIDED += backup_ram
 FEATURES_PROVIDED += cortexm_mpu
+FEATURES_PROVIDED += periph_gpio_read_output
 FEATURES_PROVIDED += periph_gpio_tamper_wake
 FEATURES_PROVIDED += periph_rtc_mem
 FEATURES_PROVIDED += periph_spi_on_qspi

cpu/saml1x/Makefile.features

@@ -5,6 +5,7 @@ CPU_CORE = cortex-m23
 
 FEATURES_PROVIDED += periph_hwrng
 FEATURES_PROVIDED += periph_gpio_fast_read
+FEATURES_PROVIDED += periph_gpio_read_output
 FEATURES_PROVIDED += periph_uart_collision
 
 include $(RIOTCPU)/sam0_common/Makefile.features

cpu/saml21/Makefile.features

@@ -4,6 +4,7 @@ CPU_CORE = cortex-m0plus
 CPU_MODELS_WITHOUT_HWRNG += samr30%
 
 FEATURES_PROVIDED += periph_gpio_fast_read
+FEATURES_PROVIDED += periph_gpio_read_output
 FEATURES_PROVIDED += periph_uart_collision
 
 # Low Power SRAM is *not* retained during Backup Sleep.

features.yaml

@@ -512,6 +512,13 @@ groups:
             Enabling this feature reduces read latency for an increase in power
             consumption. It affects both the classic GPIO API driver and the
             GPIO LL driver.
+    - name: periph_gpio_read_output
+      help: This feature is currently implemented on Microchip SAM0 based MCUs only.
+            Enabling this feature makes `gpio_read()` read back the actual pin level
+            of an output GPIO (instead of just returning the configured level).
+            This can be used to detect hardware problems (e.g. if a pin is set HIGH but
+            reads low).
+            The feature comes at the cost of slightly higher power consumption.
 
     groups:
     - title: Pin Level Peripheral GPIO API

makefiles/features_existing.inc.mk

@@ -185,6 +185,7 @@ FEATURES_EXISTING := \
     periph_gpio_ll_open_source \
     periph_gpio_ll_open_source_pull_down \
     periph_gpio_ll_switch_dir \
+    periph_gpio_read_output \
     periph_gpio_tamper_wake \
     periph_hash_md5 \
     periph_hash_sha3_256 \

tests/periph/gpio/Makefile

@@ -5,6 +5,7 @@ include ../Makefile.periph_common
 FEATURES_REQUIRED += periph_gpio
 FEATURES_OPTIONAL += periph_gpio_irq
 FEATURES_OPTIONAL += periph_gpio_fast_read
+FEATURES_OPTIONAL += periph_gpio_read_output
 FEATURES_OPTIONAL += periph_gpio_tamper_wake
 
 USEMODULE += shell_cmds_default