2 files changed, 113 insertions, 0 deletions
diff --git a/drivers/gpio/sn74x138.c b/drivers/gpio/sn74x138.c
new file mode 100644
index 0000000000..222e5db56c
--- /dev/null
+++ b/drivers/gpio/sn74x138.c
@@ -0,0 +1,65 @@
+/* Copyright 2022
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "sn74x138.h"
+#include "gpio.h"
+
+#define ADDRESS_PIN_COUNT 3
+
+#ifndef SN74X138_ADDRESS_PINS
+#    error sn74x138: no address pins defined!
+#endif
+
+static const pin_t address_pins[ADDRESS_PIN_COUNT] = SN74X138_ADDRESS_PINS;
+
+void sn74x138_init(void) {
+    for (int i = 0; i < ADDRESS_PIN_COUNT; i++) {
+        setPinOutput(address_pins[i]);
+        writePinLow(address_pins[i]);
+    }
+
+#if defined(SN74X138_E1_PIN)
+    setPinOutput(SN74X138_E1_PIN);
+    writePinHigh(SN74X138_E1_PIN);
+#endif
+
+#if defined(SN74X138_E2_PIN)
+    setPinOutput(SN74X138_E2_PIN);
+    writePinHigh(SN74X138_E2_PIN);
+#endif
+#if defined(SN74X138_E3_PIN)
+    setPinOutput(SN74X138_E3_PIN);
+    writePinLow(SN74X138_E3_PIN);
+#endif
+}
+
+void sn74x138_set_enabled(bool enabled) {
+#if defined(SN74X138_E1_PIN)
+    writePin(SN74X138_E1_PIN, !enabled);
+#endif
+#if defined(SN74X138_E2_PIN)
+    writePin(SN74X138_E2_PIN, !enabled);
+#endif
+#if defined(SN74X138_E3_PIN)
+    writePin(SN74X138_E3_PIN, enabled);
+#endif
+}
+
+void sn74x138_set_addr(uint8_t address) {
+    for (int i = 0; i < ADDRESS_PIN_COUNT; i++) {
+        writePin(address_pins[i], address & (1 << i));
+    }
+}
diff --git a/drivers/gpio/sn74x138.h b/drivers/gpio/sn74x138.h
new file mode 100644
index 0000000000..d4d0b6574d
--- /dev/null
+++ b/drivers/gpio/sn74x138.h
@@ -0,0 +1,48 @@
+/* Copyright 2022
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <stdint.h>
+#include <stdbool.h>
+
+/**
+ * Driver for 74x138 3-to-8 decoder/demultiplexer with inverting outputs
+ * https://assets.nexperia.com/documents/data-sheet/74HC_HCT138.pdf
+ */
+
+/**
+ * Initialize the address and output enable pins.
+ */
+void sn74x138_init(void);
+
+/**
+ * Set the enabled state.
+ *
+ * When enabled is true, pulls the E1 and E2 pins low, and the E3 pin high.
+ *
+ * \param enabled The enable state to set.
+ */
+void sn74x138_set_enabled(bool enabled);
+
+/**
+ * Set the output pin address.
+ * 
+ * The selected output pin will be pulled low, while the remaining output pins will be high.
+ *
+ * \param address The address to set, from 0 to 7.
+ */
+void sn74x138_set_addr(uint8_t address);