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Extend I2C implementation to deal with higher frequencies

pull/1505/head
Steven Cooreman 2016-01-15 13:14:08 +01:00
parent 45dbe35006
commit 8ea7d713d6
1 changed files with 26 additions and 2 deletions
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28
libraries/mbed/targets/hal/TARGET_Silicon_Labs/TARGET_EFM32/i2c_api.c
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@ -107,6 +107,10 @@ void i2c_init(i2c_t *obj, PinName sda, PinName scl)
I2CName i2c_scl = (I2CName) pinmap_peripheral(scl, PinMap_I2C_SCL);
obj->i2c.i2c = (I2C_TypeDef*) pinmap_merge(i2c_sda, i2c_scl);
MBED_ASSERT(((int) obj->i2c.i2c) != NC);
/* You need both SDA and SCL for I2C, so configuring one of them to NC is illegal */
MBED_ASSERT((uint32_t)sda != (uint32_t)NC);
MBED_ASSERT((uint32_t)scl != (uint32_t)NC);
/* Enable clock for the peripheral */
CMU_ClockEnable(i2c_get_clock(obj), true);
@ -131,7 +135,7 @@ void i2c_init(i2c_t *obj, PinName sda, PinName scl)
(pin_location(scl, PinMap_I2C_SCL) << _I2C_ROUTELOC0_SCLLOC_SHIFT);
#endif
/* Set up the pins for I2C use */
/* Set up the pins for I2C use: WiredAnd and high drive strength to reduce slew rate */
pin_mode(scl, WiredAndPullUp);
pin_mode(sda, WiredAndPullUp);
@ -192,7 +196,23 @@ void i2c_frequency(i2c_t *obj, int hz)
{
/* Set frequency. As the second argument is 0,
* HFPER clock frequency is used as reference freq */
I2C_BusFreqSet(obj->i2c.i2c, REFERENCE_FREQUENCY, hz, i2cClockHLRStandard);
if (hz <= 0) return;
/* In I2C Normal mode (50% duty), we can go up to 100kHz */
if (hz <= 100000) {
I2C_BusFreqSet(obj->i2c.i2c, REFERENCE_FREQUENCY, hz, i2cClockHLRStandard);
}
/* In I2C Fast mode (6:3 ratio), we can go up to 400kHz */
else if (hz <= 400000) {
I2C_BusFreqSet(obj->i2c.i2c, REFERENCE_FREQUENCY, hz, i2cClockHLRAsymetric);
}
/* In I2C Fast+ mode (11:6 ratio), we can go up to 1 MHz */
else if (hz <= 1000000) {
I2C_BusFreqSet(obj->i2c.i2c, REFERENCE_FREQUENCY, hz, i2cClockHLRFast);
}
/* Cap requested frequency at 1MHz */
else {
I2C_BusFreqSet(obj->i2c.i2c, REFERENCE_FREQUENCY, 1000000, i2cClockHLRFast);
}
}
/* Creates a start condition on the I2C bus */
@ -352,11 +372,15 @@ int block_and_wait_for_ack(I2C_TypeDef *i2c)
void i2c_slave_mode(i2c_t *obj, int enable_slave)
{
if(enable_slave) {
/* Datasheet note: DIV must be set to 1 during slave operation */
obj->i2c.i2c->DIV = 1;
obj->i2c.i2c->CTRL |= _I2C_CTRL_SLAVE_MASK;
obj->i2c.i2c->CTRL |= _I2C_CTRL_AUTOACK_MASK; //Slave implementation assumes auto acking
} else {
obj->i2c.i2c->CTRL &= ~_I2C_CTRL_SLAVE_MASK;
obj->i2c.i2c->CTRL &= ~_I2C_CTRL_AUTOACK_MASK; //Master implementation ACKs manually
/* function is only called with enable_slave = false through i2c_init(..), so frequency is
already guaranteed to be set */
}
}