1 files changed, 128 insertions, 0 deletions
diff --git a/stm/mma.c b/stm/mma.c
new file mode 100644
index 000000000..e56608ef4
--- /dev/null
+++ b/stm/mma.c
@@ -0,0 +1,128 @@
+#include <stdio.h>
+
+#include <stm32f4xx.h>
+#include <stm32f4xx_rcc.h>
+#include <stm32f4xx_gpio.h>
+
+#include "mma.h"
+
+void mma_init() {
+    RCC->APB1ENR |= RCC_APB1ENR_I2C1EN; // enable I2C1
+    //gpio_pin_init(GPIOB, 6 /* B6 is SCL */, 2 /* AF mode */, 1 /* open drain output */, 1 /* 25 MHz */, 0 /* no pull up or pull down */);
+    //gpio_pin_init(GPIOB, 7 /* B7 is SDA */, 2 /* AF mode */, 1 /* open drain output */, 1 /* 25 MHz */, 0 /* no pull up or pull down */);
+    //gpio_pin_af(GPIOB, 6, 4 /* AF 4 for I2C1 */);
+    //gpio_pin_af(GPIOB, 7, 4 /* AF 4 for I2C1 */);
+    // XXX untested GPIO init! (was above code)
+    GPIO_InitTypeDef GPIO_InitStructure;
+    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;
+    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
+    GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
+    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_25MHz;
+    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ;
+    GPIO_Init(GPIOB, &GPIO_InitStructure);
+    GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_I2C1);
+    GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_I2C1);
+
+    // get clock speeds
+    RCC_ClocksTypeDef rcc_clocks;
+    RCC_GetClocksFreq(&rcc_clocks);
+
+    // disable the I2C peripheral before we configure it
+    I2C1->CR1 &= ~I2C_CR1_PE;
+
+    // program peripheral input clock
+    I2C1->CR2 = 4; // no interrupts; 4 MHz (hopefully!) (could go up to 42MHz)
+
+    // configure clock control reg
+    uint32_t freq = rcc_clocks.PCLK1_Frequency / (100000 << 1); // want 100kHz, this is the formula for freq
+    I2C1->CCR = freq; // standard mode (speed), freq calculated as above
+
+    // configure rise time reg
+    I2C1->TRISE = (rcc_clocks.PCLK1_Frequency / 1000000) + 1; // formula for trise, gives maximum rise time
+
+    // enable the I2C peripheral
+    I2C1->CR1 |= I2C_CR1_PE;
+
+    // set START bit in CR1 to generate a start cond!
+}
+
+static uint32_t i2c_get_sr() {
+    // must read SR1 first, then SR2, as the read can clear some flags
+    uint32_t sr1 = I2C1->SR1;
+    uint32_t sr2 = I2C1->SR2;
+    return (sr2 << 16) | sr1;
+}
+
+void mma_restart(uint8_t addr, int write) {
+    // send start condition
+    I2C1->CR1 |= I2C_CR1_START;
+
+    // wait for BUSY, MSL and SB --> Slave has acknowledged start condition
+    while ((i2c_get_sr() & 0x00030001) != 0x00030001) {
+    }
+
+    if (write) {
+        // send address and write bit
+        I2C1->DR = (addr << 1) | 0;
+        // wait for BUSY, MSL, ADDR, TXE and TRA
+        while ((i2c_get_sr() & 0x00070082) != 0x00070082) {
+        }
+    } else {
+        // send address and read bit
+        I2C1->DR = (addr << 1) | 1;
+        // wait for BUSY, MSL and ADDR flags
+        while ((i2c_get_sr() & 0x00030002) != 0x00030002) {
+        }
+    }
+}
+
+void mma_start(uint8_t addr, int write) {
+    // wait until I2C is not busy
+    while (I2C1->SR2 & I2C_SR2_BUSY) {
+    }
+
+    // do rest of start
+    mma_restart(addr, write);
+}
+
+void mma_send_byte(uint8_t data) {
+    // send byte
+    I2C1->DR = data;
+    // wait for TRA, BUSY, MSL, TXE and BTF (byte transmitted)
+    int timeout = 1000000;
+    while ((i2c_get_sr() & 0x00070084) != 0x00070084) {
+        if (timeout-- <= 0) {
+            printf("mma_send_byte timed out!\n");
+            break;
+        }
+    }
+}
+
+uint8_t mma_read_ack() {
+    // enable ACK of received byte
+    I2C1->CR1 |= I2C_CR1_ACK;
+    // wait for BUSY, MSL and RXNE (byte received)
+    while ((i2c_get_sr() & 0x00030040) != 0x00030040) {
+    }
+    // read and return data
+    uint8_t data = I2C1->DR;
+    return data;
+}
+
+uint8_t mma_read_nack() {
+    // disable ACK of received byte (to indicate end of receiving)
+    I2C1->CR1 &= (uint16_t)~((uint16_t)I2C_CR1_ACK);
+    // last byte should apparently also generate a stop condition
+    I2C1->CR1 |= I2C_CR1_STOP;
+    // wait for BUSY, MSL and RXNE (byte received)
+    while ((i2c_get_sr() & 0x00030040) != 0x00030040) {
+    }
+    // read and return data
+    uint8_t data = I2C1->DR;
+    return data;
+}
+
+void mma_stop() {
+    // send stop condition
+    I2C1->CR1 |= I2C_CR1_STOP;
+}