stm32f2_f4_i2c.cpp

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/* Copyright (c) 2013 Skyward Experimental Rocketry
 * Author: Federico Terraneo
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 
#include "stm32f2_f4_i2c.h"
 
#include <kernel/scheduler/scheduler.h>
#include <miosix.h>
 
// #define I2C_WITH_DMA
 
using namespace miosix;
 
static volatile bool error;  
static Thread* waiting = 0;  
 
/* In non-DMA mode the variables below are used to
 * handle the reception of 2 or more bytes through
 * an interrupt, avoiding the thread that calls recv
 * to be locked in polling
 */
 
#ifndef I2C_WITH_DMA
static uint8_t* rxBuf         = 0;
static unsigned int rxBufCnt  = 0;
static unsigned int rxBufSize = 0;
#endif
 
#ifdef I2C_WITH_DMA
void __attribute__((naked)) DMA1_Stream0_IRQHandler()
{
    saveContext();
    asm volatile("bl _Z20I2C1rxDmaHandlerImplv");
    restoreContext();
}
 
void __attribute__((used)) I2C1rxDmaHandlerImpl()
{
    DMA1->LIFCR = DMA_LIFCR_CTCIF0 | DMA_LIFCR_CTEIF0 | DMA_LIFCR_CDMEIF0 |
                  DMA_LIFCR_CFEIF0;
    I2C1->CR1 |= I2C_CR1_STOP;
    if (waiting == 0)
        return;
    waiting->IRQwakeup();
    if (waiting->IRQgetPriority() >
        Thread::IRQgetCurrentThread()->IRQgetPriority())
    {
        Scheduler::IRQfindNextThread();
    }
    waiting = 0;
}
 
void DMA1_Stream7_IRQHandler()
{
    DMA1->HIFCR = DMA_HIFCR_CTCIF7 | DMA_HIFCR_CTEIF7 | DMA_HIFCR_CDMEIF7 |
                  DMA_HIFCR_CFEIF7;
 
    // We can't just wake the thread because the I2C is double buffered, and
    // this  interrupt is fired at the same time as the second last byte is
    // starting  to be sent out of the bus. If we return now, the main code
    // would send a  stop condiotion too soon, and the last byte would never be
    // sent. Instead,  we change from DMA mode to IRQ mode, so when the second
    // last byte is sent,  that interrupt is fired and the last byte is sent
    // out.  Note that since no thread is awakened from this IRQ, there's no
    // need for  the saveContext(), restoreContext() and __attribute__((naked))
    I2C1->CR2 &= ~I2C_CR2_DMAEN;
    I2C1->CR2 |= I2C_CR2_ITBUFEN | I2C_CR2_ITEVTEN;
}
 
#endif
 
void __attribute__((naked)) I2C1_EV_IRQHandler()
{
    saveContext();
    asm volatile("bl _Z15I2C1HandlerImplv");
    restoreContext();
}
 
void __attribute__((used)) I2C1HandlerImpl()
{
#ifdef I2C_WITH_DMA
    // When called to resolve the last byte not sent issue, clearing
    // I2C_CR2_ITBUFEN prevents this interrupt being re-entered forever, as
    // it does not send another byte to the I2C, so the interrupt would remain
    // pending. When called after the start bit has been sent, clearing
    // I2C_CR2_ITEVTEN prevents the same infinite re-enter as this interrupt
    // does not start an address transmission, which is necessary to stop
    // this interrupt from being pending
    I2C1->CR2 &= ~(I2C_CR2_ITEVTEN | I2C_CR2_ITBUFEN);
    if (waiting == 0)
        return;
#else
 
    bool rxFinished = false;
 
    /* If rxBuf is equal to zero means that we are sending the slave
       address and this ISR is used to manage the address sent interrupt */
 
    if (rxBuf == 0)
    {
        I2C1->CR2 &= ~I2C_CR2_ITEVTEN;
        rxFinished = true;
    }
 
    if (I2C1->SR1 & I2C_SR1_RXNE)
    {
        rxBuf[rxBufCnt++] = I2C1->DR;
        if (rxBufCnt >= rxBufSize)
        {
            I2C1->CR2 &= ~(I2C_CR2_ITEVTEN | I2C_CR2_ITBUFEN);
            rxFinished = true;
        }
    }
 
    if (waiting == 0 || !rxFinished)
        return;
#endif
    waiting->IRQwakeup();
    if (waiting->IRQgetPriority() >
        Thread::IRQgetCurrentThread()->IRQgetPriority())
    {
        Scheduler::IRQfindNextThread();
    }
    waiting = 0;
}
 
void __attribute__((naked)) I2C1_ER_IRQHandler()
{
    saveContext();
    asm volatile("bl _Z18I2C1errHandlerImplv");
    restoreContext();
}
 
void __attribute__((used)) I2C1errHandlerImpl()
{
    I2C1->SR1 = 0;  // Clear error flags
    error     = true;
    if (waiting == 0)
        return;
    waiting->IRQwakeup();
    if (waiting->IRQgetPriority() >
        Thread::IRQgetCurrentThread()->IRQgetPriority())
    {
        Scheduler::IRQfindNextThread();
    }
    waiting = 0;
}
 
namespace miosix
{
 
//
// class I2C
//
 
I2C1Driver& I2C1Driver::instance()
{
    static I2C1Driver singleton;
    return singleton;
}
 
void I2C1Driver::init()
{
    // I2C devices are connected to APB1, whose frequency is the system clock
    // divided by a value set in the PPRE1 bits of RCC->CFGR
    const int ppre1     = (RCC->CFGR & RCC_CFGR_PPRE1) >> 10;
    const int divFactor = (ppre1 & 1 << 2) ? (2 << (ppre1 & 0x3)) : 1;
    const int fpclk1    = SystemCoreClock / divFactor;
    // iprintf("fpclk1=%d\n",fpclk1);
 
    {
        FastInterruptDisableLock dLock;
 
#ifdef I2C_WITH_DMA
        RCC->AHB1ENR |= RCC_AHB1ENR_DMA1EN;
        RCC_SYNC();
#endif
        RCC->APB1ENR |= RCC_APB1ENR_I2C1EN;  // Enable clock gating
        RCC_SYNC();
    }
 
#ifdef I2C_WITH_DMA
    NVIC_SetPriority(DMA1_Stream7_IRQn, 10);  // Low priority for DMA
    NVIC_ClearPendingIRQ(
        DMA1_Stream7_IRQn);  // DMA1 stream 7 channel 1 = I2C1 TX
    NVIC_EnableIRQ(DMA1_Stream7_IRQn);
 
    NVIC_SetPriority(DMA1_Stream0_IRQn, 10);  // Low priority for DMA
    NVIC_ClearPendingIRQ(
        DMA1_Stream0_IRQn);  // DMA1 stream 0 channel 1 = I2C1 RX
    NVIC_EnableIRQ(DMA1_Stream0_IRQn);
#endif
 
    NVIC_SetPriority(I2C1_EV_IRQn, 10);  // Low priority for I2C
    NVIC_ClearPendingIRQ(I2C1_EV_IRQn);
    NVIC_EnableIRQ(I2C1_EV_IRQn);
 
    NVIC_SetPriority(I2C1_ER_IRQn, 10);
    NVIC_ClearPendingIRQ(I2C1_ER_IRQn);
    NVIC_EnableIRQ(I2C1_ER_IRQn);
 
    I2C1->CR1 = I2C_CR1_SWRST;
    I2C1->CR1 = 0;
    I2C1->CR2 = fpclk1 / 1000000;  // Set pclk frequency in MHz
    // This sets the duration of both Thigh and Tlow (master mode))
    const int i2cSpeed = 100000;  // 100KHz
    I2C1->CCR =
        std::max(4, fpclk1 / (2 * i2cSpeed));  // Duty=2, standard mode (100KHz)
    // Datasheet says with I2C @ 100KHz, maximum SCL rise time is 1000ns
    // Need to change formula if I2C needs to run @ 400kHz
    I2C1->TRISE = fpclk1 / 1000000 + 1;
    I2C1->CR1   = I2C_CR1_PE;  // Enable peripheral
}
 
bool I2C1Driver::send(unsigned char address, const void* data, int len,
                      bool sendStop)
{
    /* if sendStop is true user is requesting to have the stop condition sent,
     * so noStop has to be set to false
     */
    noStop = !sendStop;
 
    address &= 0xfe;  // Mask bit 0, as we are writing
    if (start(address) == false || (I2C1->SR2 & I2C_SR2_TRA) == 0)
    {
        I2C1->CR1 |= I2C_CR1_STOP;
        return false;
    }
 
#ifdef I2C_WITH_DMA
    waiting            = Thread::getCurrentThread();
    DMA1_Stream7->CR   = 0;
    DMA1_Stream7->PAR  = reinterpret_cast<unsigned int>(&I2C1->DR);
    DMA1_Stream7->M0AR = reinterpret_cast<unsigned int>(data);
    DMA1_Stream7->NDTR = len;
    DMA1_Stream7->FCR  = DMA_SxFCR_FEIE | DMA_SxFCR_DMDIS;
    DMA1_Stream7->CR   = DMA_SxCR_CHSEL_0  // Channel 1
                       | DMA_SxCR_MINC     // Increment memory pointer
                       | DMA_SxCR_DIR_0    // Memory to peripheral
                       | DMA_SxCR_TCIE     // Interrupt on transfer complete
                       | DMA_SxCR_TEIE     // Interrupt on transfer error
                       | DMA_SxCR_DMEIE    // Interrupt on direct mode error
                       | DMA_SxCR_EN;      // Start DMA
 
    // Enable DMA in the I2C peripheral *after* having configured the DMA
    // peripheral, or a spurious interrupt is triggered
    I2C1->CR2 |= I2C_CR2_DMAEN | I2C_CR2_ITERREN;
 
    {
        FastInterruptDisableLock dLock;
        while (waiting)
        {
            waiting->IRQwait();
            {
                FastInterruptEnableLock eLock(dLock);
                Thread::yield();
            }
        }
    }
 
    DMA1_Stream7->CR = 0;
 
    // The DMA interrupt routine changes the interrupt flags!
    I2C1->CR2 &= ~(I2C_CR2_ITEVTEN | I2C_CR2_ITERREN);
#else
 
    I2C1->CR2 |= I2C_CR2_ITERREN;
 
    const uint8_t* txData = reinterpret_cast<const uint8_t*>(data);
    for (int i = 0; i < len; i++)
    {
        I2C1->DR = txData[i];
        while (!(I2C1->SR1 & I2C_SR1_TXE))
            ;
    }
 
    I2C1->CR2 &= ~I2C_CR2_ITERREN;
#endif
 
    /* The main idea of this driver is to avoid having the processor spinning
     * waiting on some status flag. Why? Because I2C is slow compared to a
     * modern processor. A 120MHz core does 1200 clock cycles in the time it
     * takes to transfer a single bit through an I2C clocked at 100KHz.
     * This time could be better spent doing a context switch and letting
     * another thread do useful work, or (and Miosix does it automatically if
     * there are no ready threads) sleeping the processor core. However,
     * I'm quite disappointed by the STM32 I2C peripheral, as it seems overly
     * complicated to use. To come close to achieving this goal I had to
     * orchestrate among *four* interrupt handlers, two of the DMA, and two
     * of the I2C itself. And in the end, what's even more disappointing, is
     * that I haven't found a way to completely avoid spinning. Why?
     * There's no interrupt that's fired when the stop bit is sent!
     * And what's worse, the documentation says that after you set the stop
     * bit in the CR2 register you can't write to it again (for example, to send
     * a start bit because two i2c api calls are made back to back) until the
     * MSL bit is cleared. But there's no interrupt tied to that event!
     * What's worse, is that the closest interrupt flag I've found when doing
     * an I2C send is fired when the last byte is *beginning* to be sent.
     * Maybe I haven't searched well enough, but the fact is I found nothing,
     * so this code below spins for 8 data bits of the last byte plus the ack
     * bit, plus the stop bit. That's 12000 wasted CPU cycles. Thanks, ST...
     */
 
    if (sendStop)
    {
        I2C1->CR1 |= I2C_CR1_STOP;
        while (I2C1->SR2 & I2C_SR2_MSL)
            ;  // Wait for stop bit sent
    }
    else
    {
        // Dummy write, is the only way to clear
        // the TxE flag if stop bit is not sent...
        I2C1->DR = 0x00;
    }
 
    return true;
}
 
bool I2C1Driver::recv(unsigned char address, void* data, int len)
{
    address |= 0x01;
    if (start(address, len == 1) == false || I2C1->SR2 & I2C_SR2_TRA)
    {
        I2C1->CR1 |= I2C_CR1_STOP;
        return false;
    }
 
    error   = false;
    waiting = Thread::getCurrentThread();
 
#ifdef I2C_WITH_DMA
    I2C1->CR2 |= I2C_CR2_DMAEN | I2C_CR2_LAST | I2C_CR2_ITERREN;
 
    DMA1_Stream0->CR   = 0;
    DMA1_Stream0->PAR  = reinterpret_cast<unsigned int>(&I2C1->DR);
    DMA1_Stream0->M0AR = reinterpret_cast<unsigned int>(data);
    DMA1_Stream0->NDTR = len;
    DMA1_Stream0->FCR  = DMA_SxFCR_FEIE | DMA_SxFCR_DMDIS;
    DMA1_Stream0->CR   = DMA_SxCR_CHSEL_0  // Channel 1
                       | DMA_SxCR_MINC     // Increment memory pointer
                       | DMA_SxCR_TCIE     // Interrupt on transfer complete
                       | DMA_SxCR_TEIE     // Interrupt on transfer error
                       | DMA_SxCR_DMEIE    // Interrupt on direct mode error
                       | DMA_SxCR_EN;      // Start DMA
 
    {
        FastInterruptDisableLock dLock;
        while (waiting)
        {
            waiting->IRQwait();
 
            {
                FastInterruptEnableLock eLock(dLock);
                Thread::yield();
            }
        }
    }
 
    DMA1_Stream7->CR = 0;
 
    I2C1->CR2 &= ~(I2C_CR2_DMAEN | I2C_CR2_LAST | I2C_CR2_ITERREN);
 
#else
 
    /* Since i2c data reception is a bit tricky (see ST's reference manual for
     * further details), the thread that calls recv is yelded and reception is
     * handled using interrupts only if the number of bytes to be received is
     * greater than one.
     */
 
    rxBuf = reinterpret_cast<uint8_t*>(data);
 
    if (len > 1)
    {
        I2C1->CR2 |= I2C_CR2_ITERREN | I2C_CR2_ITEVTEN | I2C_CR2_ITBUFEN;
 
        rxBufCnt  = 0;
        rxBufSize = len - 2;
 
        {
            FastInterruptDisableLock dLock;
            while (waiting)
            {
                waiting->IRQwait();
                {
                    FastInterruptEnableLock eLock(dLock);
                    Thread::yield();
                }
            }
        }
        I2C1->CR2 &= ~(I2C_CR2_ITEVTEN | I2C_CR2_ITBUFEN);
    }
 
    I2C1->CR1 &= ~I2C_CR1_ACK;
    I2C1->CR1 |= I2C_CR1_STOP;
 
    while (!(I2C1->SR1 & I2C_SR1_RXNE))
        ;
    rxBuf[len - 1] = I2C1->DR;
 
    // set pointer to rx buffer to zero after having used it, see i2c event ISR
    rxBuf = 0;
 
    I2C1->CR2 &= ~I2C_CR2_ITERREN;
#endif
 
    while (I2C1->SR2 & I2C_SR2_MSL)
        ;  // Wait for stop bit sent
    return !error;
}
 
bool I2C1Driver::start(unsigned char address, bool immediateNak)
{
    /* Because the only way to send a restart is having the send function not
     * sending a stop condition after the data transfer, here we have to manage
     * a couple of things in SR1:
     * - the BTF flag is set, cleared by a dummy read of DR
     * - The Berr flag is set, this because the I2C harware detects the start
     *   condition sent without a stop before it as a misplaced start and
     *   rises an error
     */
 
    I2C1->CR1 |= I2C_CR1_START | I2C_CR1_ACK;
    if (!waitStatus1())
        return false;
    if ((I2C1->SR1 & I2C_SR1_SB) == 0)
        return false;  // Must read SR1 to clear flag
    I2C1->DR = address;
    if (immediateNak)
        I2C1->CR1 &= ~I2C_CR1_ACK;
    if (!waitStatus1())
        return false;
    if (I2C1->SR1 & I2C_SR1_AF)
        return false;  // Must read SR1 and SR2
    if ((I2C1->SR2 & I2C_SR2_MSL) == 0)
        return false;
    return true;
}
 
bool I2C1Driver::waitStatus1()
{
    error   = false;
    waiting = Thread::getCurrentThread();
    I2C1->CR2 |= I2C_CR2_ITEVTEN | I2C_CR2_ITERREN;
    {
        FastInterruptDisableLock dLock;
        while (waiting)
        {
            waiting->IRQwait();
            {
                FastInterruptEnableLock eLock(dLock);
                Thread::yield();
            }
        }
    }
    I2C1->CR2 &= ~(I2C_CR2_ITEVTEN | I2C_CR2_ITERREN);
    return !error;
}
 
}  // namespace miosix