1 files changed, 27 insertions, 0 deletions
diff --git a/src/stm32f4/gpio.c b/src/stm32f4/gpio.c
new file mode 100644
index 00000000..370aba1f
--- /dev/null
+++ b/src/stm32f4/gpio.c
@@ -0,0 +1,27 @@
+// GPIO functions on stm32f4
+//
+// Copyright (C) 2019  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include "internal.h" // gpio_peripheral
+
+static GPIO_TypeDef * const digital_regs[] = {
+    GPIOA, GPIOB, GPIOC
+};
+
+// Set the mode and extended function of a pin
+void
+gpio_peripheral(uint32_t gpio, uint32_t mode, uint32_t func, int pullup)
+{
+    GPIO_TypeDef *regs = digital_regs[GPIO2PORT(gpio)];
+    uint32_t pup = pullup ? (pullup > 0 ? 1 : 2) : 0;
+    uint32_t pos = gpio % 16, af_reg = pos / 8;
+    uint32_t af_shift = (pos % 8) * 4, af_msk = 0x0f << af_shift;
+    uint32_t m_shift = pos * 2, m_msk = 0x03 << m_shift;
+
+    regs->AFR[af_reg] = (regs->AFR[af_reg] & ~af_msk) | (func << af_shift);
+    regs->MODER = (regs->MODER & ~m_msk) | (mode << m_shift);
+    regs->PUPDR = (regs->PUPDR & ~m_msk) | (pup << m_shift);
+    regs->OSPEEDR = (regs->OSPEEDR & ~m_msk) | (0x02 << m_shift);
+}