Added i2c python interface object

stm/i2c.c

+#include <stdio.h>
+
+#include <stm32f4xx.h>
+#include <stm32f4xx_rcc.h>
+#include <stm32f4xx_gpio.h>
+
+#include "misc.h"
+#include "systick.h"
+#include "mpconfig.h"
+#include "obj.h"
+
+typedef enum {
+    PYB_I2C_1 = 0,
+    PYB_I2C_2 = 1,
+} pyb_i2c_t;
+
+typedef enum {
+	I2C_STATE_IDLE = 0,
+	I2C_STATE_WRITE = 1,
+	I2C_STATE_READ = 2,
+} i2c_state_t;
+
+// set to true if the port has already been initialized
+bool i2c1_port_initialized = false;
+bool i2c2_port_initialized = false;
+
+static I2C_TypeDef * _i2c_port_addr(pyb_i2c_t i2c_port)
+{
+	if (i2c_port == PYB_I2C_1)
+		return I2C1;
+	if (i2c_port == PYB_I2C_2)
+		return I2C2;
+	return NULL;
+}
+
+// todo - perhaps there should be some global resource management for gpio
+// this function would fail if the i2c pins have already been defined for
+// use by another python object
+// as it is, this always returns true (unless i2c_port is invalid)
+static bool _i2c_init (pyb_i2c_t i2c_port)
+{
+    GPIO_InitTypeDef GPIO_InitStructure;
+
+	I2C_TypeDef *i2c = _i2c_port_addr(i2c_port);
+	if (i2c == NULL)
+		return false;
+
+	if (i2c_port == PYB_I2C_1) {
+		if (i2c1_port_initialized == true) return true;
+		RCC->APB1ENR |= RCC_APB1ENR_I2C1EN; // enable I2C1
+
+	    // PB6=SCL, PB7=SDA
+	    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);
+
+	    // alternate functions for SCL and SDA
+	    GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_I2C1);
+	    GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_I2C1);
+
+
+		i2c1_port_initialized = true;
+	}
+
+	if (i2c_port == PYB_I2C_2) {
+		if (i2c2_port_initialized == true) return true;
+		RCC->APB1ENR |= RCC_APB1ENR_I2C2EN; // enable I2C2
+
+		// PB10=SCL, PB11=SDA
+	    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10 | GPIO_Pin_11;
+	    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);
+
+	    // alternate functions for SCL and SDA
+	    GPIO_PinAFConfig(GPIOB, GPIO_PinSource10, GPIO_AF_I2C2);
+	    GPIO_PinAFConfig(GPIOB, GPIO_PinSource11, GPIO_AF_I2C2);
+
+
+		i2c2_port_initialized = true;
+	}
+
+    // get clock speeds
+    RCC_ClocksTypeDef rcc_clocks;
+    RCC_GetClocksFreq(&rcc_clocks);
+
+    // disable the I2C peripheral before we configure it
+    i2c->CR1 &= ~I2C_CR1_PE;
+
+    // program peripheral input clock
+    i2c->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
+    i2c->CCR = freq; // standard mode (speed), freq calculated as above
+
+    // configure rise time reg
+    i2c->TRISE = (rcc_clocks.PCLK1_Frequency / 1000000) + 1; // formula for trise, gives maximum rise time
+
+    // enable the I2C peripheral
+    i2c->CR1 |= I2C_CR1_PE;
+
+
+	return true;
+}
+
+static uint32_t _i2c_get_sr(pyb_i2c_t i2c_port) {
+    // must read SR1 first, then SR2, as the read can clear some flags
+	I2C_TypeDef *i2c = _i2c_port_addr(i2c_port);
+	if (i2c == NULL) return 0;
+
+    uint32_t sr1 = i2c->SR1;
+    uint32_t sr2 = i2c->SR2;
+    return (sr2 << 16) | sr1;
+}
+
+static bool _i2c_restart(pyb_i2c_t i2c_port, uint8_t addr, int write) {
+	I2C_TypeDef *i2c = _i2c_port_addr(i2c_port);
+	if (i2c == NULL) return false;
+
+    // send start condition
+    i2c->CR1 |= I2C_CR1_START;
+
+    // wait for BUSY, MSL and SB --> Slave has acknowledged start condition
+    uint32_t timeout = 1000000;
+    while ((_i2c_get_sr(i2c_port) & 0x00030001) != 0x00030001) {
+        if (--timeout == 0) {
+            //printf("timeout in _i2c_restart\n");
+            return false;
+        }
+    }
+
+    if (write) {
+        // send address and write bit
+        i2c->DR = (addr << 1) | 0;
+        // wait for BUSY, MSL, ADDR, TXE and TRA
+        timeout = 1000000;
+        while ((_i2c_get_sr(i2c_port) & 0x00070082) != 0x00070082) {
+            if (--timeout == 0) {
+                //printf("timeout in _i2c_restart write\n");
+                return false;
+            }
+        }
+    } else {
+        // send address and read bit
+        i2c->DR = (addr << 1) | 1;
+        // wait for BUSY, MSL and ADDR flags
+        timeout = 1000000;
+        while ((_i2c_get_sr(i2c_port) & 0x00030002) != 0x00030002) {
+            if (--timeout == 0) {
+                //printf("timeout in _i2c_restart read\n");
+                return false;
+            }
+        }
+    }
+    return true;
+}
+
+static bool _i2c_send_byte(pyb_i2c_t i2c_port, uint8_t data) {
+	I2C_TypeDef *i2c = _i2c_port_addr(i2c_port);
+	if (i2c == NULL) return false;
+
+    // send byte
+    i2c->DR = data;
+    // wait for TRA, BUSY, MSL, TXE and BTF (byte transmitted)
+    uint32_t timeout = 1000000;
+    while ((_i2c_get_sr(i2c_port) & 0x00070084) != 0x00070084) {
+        if (--timeout == 0) {
+            //printf("timeout in _i2c_send_byte\n");
+            return false;
+        }
+    }
+    return true;
+}
+
+static uint8_t _i2c_read_ack(pyb_i2c_t i2c_port) {
+	I2C_TypeDef *i2c = _i2c_port_addr(i2c_port);
+	if (i2c == NULL) return 0;
+
+    // enable ACK of received byte
+    i2c->CR1 |= I2C_CR1_ACK;
+    // wait for BUSY, MSL and RXNE (byte received)
+    uint32_t timeout = 1000000;
+    while ((_i2c_get_sr(i2c_port) & 0x00030040) != 0x00030040) {
+        if (--timeout == 0) {
+            //printf("timeout in _i2c_read_ack\n");
+            break;
+        }
+    }
+    // read and return data
+    uint8_t data = i2c->DR;
+    return data;
+}
+
+static uint8_t _i2c_read_nack(pyb_i2c_t i2c_port) {
+	I2C_TypeDef *i2c = _i2c_port_addr(i2c_port);
+	if (i2c == NULL) return 0;
+
+    // disable ACK of received byte (to indicate end of receiving)
+    i2c->CR1 &= (uint16_t)~((uint16_t)I2C_CR1_ACK);
+    // last byte should apparently also generate a stop condition
+    i2c->CR1 |= I2C_CR1_STOP;
+    // wait for BUSY, MSL and RXNE (byte received)
+    uint32_t timeout = 1000000;
+    while ((_i2c_get_sr(i2c_port) & 0x00030040) != 0x00030040) {
+        if (--timeout == 0) {
+            //printf("timeout in _i2c_read_nack\n");
+            break;
+        }
+    }
+    // read and return data
+    uint8_t data = i2c->DR;
+    return data;
+}
+
+static bool _i2c_start(pyb_i2c_t i2c_port) {
+	I2C_TypeDef *i2c = _i2c_port_addr(i2c_port);
+	if (i2c == NULL) return false;
+
+    // wait until I2C is not busy
+    uint32_t timeout = 1000000;
+    while (i2c->SR2 & I2C_SR2_BUSY) {
+        if (--timeout == 0) {
+            return false;
+        }
+    }
+    return true;
+}
+
+static void _i2c_stop(pyb_i2c_t i2c_port) {
+	I2C_TypeDef *i2c = _i2c_port_addr(i2c_port);
+	if (i2c == NULL) return;
+
+    // send stop condition
+    i2c->CR1 |= I2C_CR1_STOP;
+}
+
+/******************************************************************************/
+/* Micro Python bindings                                                      */
+
+typedef struct _pyb_i2c_obj_t {
+    mp_obj_base_t base;
+    pyb_i2c_t i2c_port;
+    int i2c_addr;
+    i2c_state_t i2c_state;
+} pyb_i2c_obj_t;
+
+void i2c_obj_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in) {
+    pyb_i2c_obj_t *self = self_in;
+    print(env, "<I2C%lu addr:%lu>", (unsigned int)self->i2c_port, (unsigned int)self->i2c_addr);
+}
+
+// calls _i2c_start with write=0,1 depending on LSB of i2c_addr
+mp_obj_t i2c_obj_start(mp_obj_t self_in) {
+    pyb_i2c_obj_t *self = self_in;
+    if (self->i2c_state != I2C_STATE_IDLE) {
+    	_i2c_stop(self->i2c_port);
+    	self->i2c_state = I2C_STATE_IDLE;
+    }
+    if (_i2c_start(self->i2c_port) == true)
+    	return mp_const_true;
+    return mp_const_false;
+}
+
+mp_obj_t i2c_obj_write(mp_obj_t self_in, mp_obj_t data_in) {
+    pyb_i2c_obj_t *self = self_in;
+	if (self->i2c_state != I2C_STATE_WRITE) {
+		if (_i2c_restart(self->i2c_port, self->i2c_addr, 1) == false) {
+			_i2c_stop(self->i2c_port);
+			self->i2c_state = I2C_STATE_IDLE;
+			return mp_const_false;
+		}
+		self->i2c_state = I2C_STATE_WRITE;
+	}
+	uint8_t data = mp_obj_get_int(data_in);
+	if (_i2c_send_byte(self->i2c_port, data) == false)
+		return mp_const_false;
+	return mp_const_true;
+}
+
+mp_obj_t i2c_obj_read(mp_obj_t self_in) {
+    pyb_i2c_obj_t *self = self_in;
+	if (self->i2c_state != I2C_STATE_READ) {
+		if (_i2c_restart(self->i2c_port, self->i2c_addr, 0) == false) {
+			_i2c_stop(self->i2c_port);
+			self->i2c_state = I2C_STATE_IDLE;
+			return mp_const_false;
+		}
+		self->i2c_state = I2C_STATE_READ;
+	}
+	uint8_t data = _i2c_read_ack(self->i2c_port);
+	return mp_obj_new_int(data);
+}
+
+mp_obj_t i2c_obj_readAndStop(mp_obj_t self_in) {
+    pyb_i2c_obj_t *self = self_in;
+	if (self->i2c_state != I2C_STATE_READ) {
+		if (_i2c_restart(self->i2c_port, self->i2c_addr, 0) == false) {
+			_i2c_stop(self->i2c_port);
+			self->i2c_state = I2C_STATE_IDLE;
+			return mp_const_false;
+		}
+	}
+	uint8_t data = _i2c_read_nack(self->i2c_port);
+	self->i2c_state = I2C_STATE_IDLE;
+	return mp_obj_new_int(data);
+}
+
+mp_obj_t i2c_obj_stop(mp_obj_t self_in) {
+    pyb_i2c_obj_t *self = self_in;
+	_i2c_stop(self->i2c_port);
+	self->i2c_state = I2C_STATE_IDLE;
+    return mp_const_none;
+}
+
+static MP_DEFINE_CONST_FUN_OBJ_1(i2c_obj_start_obj, i2c_obj_start);
+static MP_DEFINE_CONST_FUN_OBJ_2(i2c_obj_write_obj, i2c_obj_write);
+static MP_DEFINE_CONST_FUN_OBJ_1(i2c_obj_read_obj, i2c_obj_read);
+static MP_DEFINE_CONST_FUN_OBJ_1(i2c_obj_readAndStop_obj, i2c_obj_readAndStop);
+static MP_DEFINE_CONST_FUN_OBJ_1(i2c_obj_stop_obj, i2c_obj_stop);
+
+static const mp_obj_type_t i2c_obj_type = {
+    { &mp_const_type },
+    "I2C",
+    i2c_obj_print, // print
+    NULL, // call_n
+    NULL, // unary_op
+    NULL, // binary_op
+    NULL, // getiter
+    NULL, // iternext
+    { // method list
+        { "start", &i2c_obj_start_obj },
+		{ "write", &i2c_obj_write_obj },
+		{ "read", &i2c_obj_read_obj },
+		{ "readAndStop", &i2c_obj_readAndStop_obj },
+        { "stop", &i2c_obj_stop_obj },
+        { NULL, NULL },
+    }
+};
+
+// create the I2C object
+// currently support either I2C1 (i2c_id = 0) or I2C2 (i2c_id = 1)
+
+mp_obj_t pyb_I2C(mp_obj_t i2c_id, mp_obj_t i2c_addr) {
+	pyb_i2c_t i2c_port;
+	switch(mp_obj_get_int(i2c_id)) {
+		case 0: i2c_port = PYB_I2C_1; break;
+		case 1: i2c_port = PYB_I2C_2; break;
+		default: return mp_const_none;
+	}
+	if (_i2c_init(i2c_port) == false)
+		return mp_const_none;
+    pyb_i2c_obj_t *o = m_new_obj(pyb_i2c_obj_t);
+    o->base.type = &i2c_obj_type;
+    o->i2c_port = i2c_port;
+    o->i2c_addr = mp_obj_get_int(i2c_addr);
+    o->i2c_state = I2C_STATE_IDLE;
+    return o;
+}

stm/i2c.h

+mp_obj_t pyb_I2C(mp_obj_t i2c_id, mp_obj_t i2c_addr);