Added i2c python interface object
Hagen Kaye
parent
b8ecc29f3b
commit
6474598c65
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#include <stdio.h>
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#include <stm32f4xx.h>
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#include <stm32f4xx_rcc.h>
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#include <stm32f4xx_gpio.h>
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#include "misc.h"
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#include "systick.h"
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#include "mpconfig.h"
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#include "obj.h"
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typedef enum {
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PYB_I2C_1 = 0,
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PYB_I2C_2 = 1,
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} pyb_i2c_t;
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typedef enum {
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I2C_STATE_IDLE = 0,
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I2C_STATE_WRITE = 1,
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I2C_STATE_READ = 2,
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} i2c_state_t;
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// set to true if the port has already been initialized
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bool i2c1_port_initialized = false;
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bool i2c2_port_initialized = false;
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static I2C_TypeDef * _i2c_port_addr(pyb_i2c_t i2c_port)
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{
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if (i2c_port == PYB_I2C_1)
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return I2C1;
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if (i2c_port == PYB_I2C_2)
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return I2C2;
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return NULL;
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}
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// todo - perhaps there should be some global resource management for gpio
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// this function would fail if the i2c pins have already been defined for
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// use by another python object
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// as it is, this always returns true (unless i2c_port is invalid)
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static bool _i2c_init (pyb_i2c_t i2c_port)
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{
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GPIO_InitTypeDef GPIO_InitStructure;
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I2C_TypeDef *i2c = _i2c_port_addr(i2c_port);
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if (i2c == NULL)
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return false;
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if (i2c_port == PYB_I2C_1) {
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if (i2c1_port_initialized == true) return true;
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RCC->APB1ENR |= RCC_APB1ENR_I2C1EN; // enable I2C1
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// PB6=SCL, PB7=SDA
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GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;
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GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
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GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
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GPIO_InitStructure.GPIO_Speed = GPIO_Speed_25MHz;
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GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
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GPIO_Init(GPIOB, &GPIO_InitStructure);
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// alternate functions for SCL and SDA
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GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_I2C1);
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GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_I2C1);
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i2c1_port_initialized = true;
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}
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if (i2c_port == PYB_I2C_2) {
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if (i2c2_port_initialized == true) return true;
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RCC->APB1ENR |= RCC_APB1ENR_I2C2EN; // enable I2C2
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// PB10=SCL, PB11=SDA
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GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10 | GPIO_Pin_11;
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GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
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GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
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GPIO_InitStructure.GPIO_Speed = GPIO_Speed_25MHz;
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GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
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GPIO_Init(GPIOB, &GPIO_InitStructure);
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// alternate functions for SCL and SDA
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GPIO_PinAFConfig(GPIOB, GPIO_PinSource10, GPIO_AF_I2C2);
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GPIO_PinAFConfig(GPIOB, GPIO_PinSource11, GPIO_AF_I2C2);
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i2c2_port_initialized = true;
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}
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// get clock speeds
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RCC_ClocksTypeDef rcc_clocks;
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RCC_GetClocksFreq(&rcc_clocks);
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// disable the I2C peripheral before we configure it
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i2c->CR1 &= ~I2C_CR1_PE;
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// program peripheral input clock
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i2c->CR2 = 4; // no interrupts; 4 MHz (hopefully!) (could go up to 42MHz)
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// configure clock control reg
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uint32_t freq = rcc_clocks.PCLK1_Frequency / (100000 << 1); // want 100kHz, this is the formula for freq
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i2c->CCR = freq; // standard mode (speed), freq calculated as above
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// configure rise time reg
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i2c->TRISE = (rcc_clocks.PCLK1_Frequency / 1000000) + 1; // formula for trise, gives maximum rise time
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// enable the I2C peripheral
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i2c->CR1 |= I2C_CR1_PE;
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return true;
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}
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static uint32_t _i2c_get_sr(pyb_i2c_t i2c_port) {
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// must read SR1 first, then SR2, as the read can clear some flags
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I2C_TypeDef *i2c = _i2c_port_addr(i2c_port);
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if (i2c == NULL) return 0;
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uint32_t sr1 = i2c->SR1;
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uint32_t sr2 = i2c->SR2;
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return (sr2 << 16) | sr1;
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}
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static bool _i2c_restart(pyb_i2c_t i2c_port, uint8_t addr, int write) {
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I2C_TypeDef *i2c = _i2c_port_addr(i2c_port);
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if (i2c == NULL) return false;
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// send start condition
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i2c->CR1 |= I2C_CR1_START;
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// wait for BUSY, MSL and SB --> Slave has acknowledged start condition
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uint32_t timeout = 1000000;
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while ((_i2c_get_sr(i2c_port) & 0x00030001) != 0x00030001) {
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if (--timeout == 0) {
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//printf("timeout in _i2c_restart\n");
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return false;
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}
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}
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if (write) {
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// send address and write bit
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i2c->DR = (addr << 1) | 0;
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// wait for BUSY, MSL, ADDR, TXE and TRA
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timeout = 1000000;
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while ((_i2c_get_sr(i2c_port) & 0x00070082) != 0x00070082) {
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if (--timeout == 0) {
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//printf("timeout in _i2c_restart write\n");
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return false;
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}
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}
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} else {
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// send address and read bit
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i2c->DR = (addr << 1) | 1;
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// wait for BUSY, MSL and ADDR flags
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timeout = 1000000;
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while ((_i2c_get_sr(i2c_port) & 0x00030002) != 0x00030002) {
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if (--timeout == 0) {
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//printf("timeout in _i2c_restart read\n");
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return false;
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}
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}
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}
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return true;
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}
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static bool _i2c_send_byte(pyb_i2c_t i2c_port, uint8_t data) {
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I2C_TypeDef *i2c = _i2c_port_addr(i2c_port);
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if (i2c == NULL) return false;
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// send byte
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i2c->DR = data;
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// wait for TRA, BUSY, MSL, TXE and BTF (byte transmitted)
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uint32_t timeout = 1000000;
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while ((_i2c_get_sr(i2c_port) & 0x00070084) != 0x00070084) {
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if (--timeout == 0) {
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//printf("timeout in _i2c_send_byte\n");
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return false;
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}
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}
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return true;
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}
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static uint8_t _i2c_read_ack(pyb_i2c_t i2c_port) {
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I2C_TypeDef *i2c = _i2c_port_addr(i2c_port);
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if (i2c == NULL) return 0;
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// enable ACK of received byte
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i2c->CR1 |= I2C_CR1_ACK;
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// wait for BUSY, MSL and RXNE (byte received)
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uint32_t timeout = 1000000;
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while ((_i2c_get_sr(i2c_port) & 0x00030040) != 0x00030040) {
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if (--timeout == 0) {
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//printf("timeout in _i2c_read_ack\n");
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break;
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}
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}
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// read and return data
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uint8_t data = i2c->DR;
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return data;
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}
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static uint8_t _i2c_read_nack(pyb_i2c_t i2c_port) {
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I2C_TypeDef *i2c = _i2c_port_addr(i2c_port);
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if (i2c == NULL) return 0;
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// disable ACK of received byte (to indicate end of receiving)
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i2c->CR1 &= (uint16_t)~((uint16_t)I2C_CR1_ACK);
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// last byte should apparently also generate a stop condition
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i2c->CR1 |= I2C_CR1_STOP;
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// wait for BUSY, MSL and RXNE (byte received)
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uint32_t timeout = 1000000;
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while ((_i2c_get_sr(i2c_port) & 0x00030040) != 0x00030040) {
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if (--timeout == 0) {
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//printf("timeout in _i2c_read_nack\n");
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break;
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}
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}
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// read and return data
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uint8_t data = i2c->DR;
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return data;
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}
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static bool _i2c_start(pyb_i2c_t i2c_port) {
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I2C_TypeDef *i2c = _i2c_port_addr(i2c_port);
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if (i2c == NULL) return false;
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// wait until I2C is not busy
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uint32_t timeout = 1000000;
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while (i2c->SR2 & I2C_SR2_BUSY) {
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if (--timeout == 0) {
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return false;
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}
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}
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return true;
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}
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static void _i2c_stop(pyb_i2c_t i2c_port) {
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I2C_TypeDef *i2c = _i2c_port_addr(i2c_port);
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if (i2c == NULL) return;
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// send stop condition
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i2c->CR1 |= I2C_CR1_STOP;
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}
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/******************************************************************************/
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/* Micro Python bindings */
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typedef struct _pyb_i2c_obj_t {
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mp_obj_base_t base;
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pyb_i2c_t i2c_port;
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int i2c_addr;
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i2c_state_t i2c_state;
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} pyb_i2c_obj_t;
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void i2c_obj_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in) {
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pyb_i2c_obj_t *self = self_in;
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print(env, "<I2C%lu addr:%lu>", (unsigned int)self->i2c_port, (unsigned int)self->i2c_addr);
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}
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// calls _i2c_start with write=0,1 depending on LSB of i2c_addr
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mp_obj_t i2c_obj_start(mp_obj_t self_in) {
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pyb_i2c_obj_t *self = self_in;
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if (self->i2c_state != I2C_STATE_IDLE) {
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_i2c_stop(self->i2c_port);
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self->i2c_state = I2C_STATE_IDLE;
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}
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if (_i2c_start(self->i2c_port) == true)
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return mp_const_true;
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return mp_const_false;
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}
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mp_obj_t i2c_obj_write(mp_obj_t self_in, mp_obj_t data_in) {
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pyb_i2c_obj_t *self = self_in;
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if (self->i2c_state != I2C_STATE_WRITE) {
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if (_i2c_restart(self->i2c_port, self->i2c_addr, 1) == false) {
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_i2c_stop(self->i2c_port);
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self->i2c_state = I2C_STATE_IDLE;
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return mp_const_false;
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}
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self->i2c_state = I2C_STATE_WRITE;
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}
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uint8_t data = mp_obj_get_int(data_in);
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if (_i2c_send_byte(self->i2c_port, data) == false)
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return mp_const_false;
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return mp_const_true;
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}
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mp_obj_t i2c_obj_read(mp_obj_t self_in) {
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pyb_i2c_obj_t *self = self_in;
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if (self->i2c_state != I2C_STATE_READ) {
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if (_i2c_restart(self->i2c_port, self->i2c_addr, 0) == false) {
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_i2c_stop(self->i2c_port);
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self->i2c_state = I2C_STATE_IDLE;
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return mp_const_false;
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}
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self->i2c_state = I2C_STATE_READ;
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}
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uint8_t data = _i2c_read_ack(self->i2c_port);
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return mp_obj_new_int(data);
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}
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mp_obj_t i2c_obj_readAndStop(mp_obj_t self_in) {
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pyb_i2c_obj_t *self = self_in;
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if (self->i2c_state != I2C_STATE_READ) {
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if (_i2c_restart(self->i2c_port, self->i2c_addr, 0) == false) {
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_i2c_stop(self->i2c_port);
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self->i2c_state = I2C_STATE_IDLE;
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return mp_const_false;
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}
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}
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uint8_t data = _i2c_read_nack(self->i2c_port);
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self->i2c_state = I2C_STATE_IDLE;
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return mp_obj_new_int(data);
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}
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mp_obj_t i2c_obj_stop(mp_obj_t self_in) {
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pyb_i2c_obj_t *self = self_in;
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_i2c_stop(self->i2c_port);
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self->i2c_state = I2C_STATE_IDLE;
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return mp_const_none;
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}
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static MP_DEFINE_CONST_FUN_OBJ_1(i2c_obj_start_obj, i2c_obj_start);
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static MP_DEFINE_CONST_FUN_OBJ_2(i2c_obj_write_obj, i2c_obj_write);
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static MP_DEFINE_CONST_FUN_OBJ_1(i2c_obj_read_obj, i2c_obj_read);
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static MP_DEFINE_CONST_FUN_OBJ_1(i2c_obj_readAndStop_obj, i2c_obj_readAndStop);
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static MP_DEFINE_CONST_FUN_OBJ_1(i2c_obj_stop_obj, i2c_obj_stop);
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static const mp_obj_type_t i2c_obj_type = {
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{ &mp_const_type },
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"I2C",
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i2c_obj_print, // print
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NULL, // call_n
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NULL, // unary_op
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NULL, // binary_op
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NULL, // getiter
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NULL, // iternext
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{ // method list
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{ "start", &i2c_obj_start_obj },
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{ "write", &i2c_obj_write_obj },
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{ "read", &i2c_obj_read_obj },
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{ "readAndStop", &i2c_obj_readAndStop_obj },
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{ "stop", &i2c_obj_stop_obj },
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{ NULL, NULL },
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}
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};
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// create the I2C object
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// currently support either I2C1 (i2c_id = 0) or I2C2 (i2c_id = 1)
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mp_obj_t pyb_I2C(mp_obj_t i2c_id, mp_obj_t i2c_addr) {
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pyb_i2c_t i2c_port;
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switch(mp_obj_get_int(i2c_id)) {
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case 0: i2c_port = PYB_I2C_1; break;
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case 1: i2c_port = PYB_I2C_2; break;
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default: return mp_const_none;
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}
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if (_i2c_init(i2c_port) == false)
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return mp_const_none;
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pyb_i2c_obj_t *o = m_new_obj(pyb_i2c_obj_t);
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o->base.type = &i2c_obj_type;
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o->i2c_port = i2c_port;
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o->i2c_addr = mp_obj_get_int(i2c_addr);
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o->i2c_state = I2C_STATE_IDLE;
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return o;
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}
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