diff options
Diffstat (limited to 'firmware/libboard/qmod/source/i2c.c')
| -rw-r--r-- | firmware/libboard/qmod/source/i2c.c | 203 |
1 files changed, 203 insertions, 0 deletions
diff --git a/firmware/libboard/qmod/source/i2c.c b/firmware/libboard/qmod/source/i2c.c new file mode 100644 index 0000000..0549da1 --- /dev/null +++ b/firmware/libboard/qmod/source/i2c.c @@ -0,0 +1,203 @@ +#include "board.h" +#include <stdbool.h> + +/* Low-Level I2C Routines */ + +static const Pin pin_sda = {PIO_PA30, PIOA, ID_PIOA, PIO_OUTPUT_1, PIO_OPENDRAIN }; +static const Pin pin_sda_in = {PIO_PA30, PIOA, ID_PIOA, PIO_INPUT, PIO_DEFAULT }; +static const Pin pin_scl = {PIO_PA31, PIOA, ID_PIOA, PIO_OUTPUT_1, PIO_OPENDRAIN }; + +static void i2c_delay() +{ + volatile int v; + int i; + + /* 100 cycles results in SCL peak length of 44us, so it's about + * 440ns per cycle here */ + for (i = 0; i < 14; i++) { + v = 0; + } +} + +void i2c_pin_init(void) +{ + PIO_Configure(&pin_scl, PIO_LISTSIZE(pin_scl)); + PIO_Configure(&pin_sda, PIO_LISTSIZE(pin_sda)); +} + +static void set_scl(void) +{ + PIO_Set(&pin_scl); + i2c_delay(); +} + +static void set_sda(void) +{ + PIO_Set(&pin_sda); + i2c_delay(); +} + +static void clear_scl(void) +{ + PIO_Clear(&pin_scl); + i2c_delay(); +} + +static void clear_sda(void) +{ + PIO_Clear(&pin_sda); + i2c_delay(); +} + +static bool read_sda(void) +{ + bool ret; + + PIO_Configure(&pin_sda_in, PIO_LISTSIZE(pin_sda_in)); + if (PIO_Get(&pin_sda_in)) + ret = true; + else + ret = false; + PIO_Configure(&pin_sda, PIO_LISTSIZE(pin_sda)); + + return ret; +} + +/* Core I2C Routines */ + +static bool i2c_started = false; + +static void i2c_start_cond(void) +{ + if (i2c_started) { + set_sda(); + set_scl(); + } + + clear_sda(); + i2c_delay(); + clear_scl(); + i2c_started = true; +} + +static void i2c_stop_cond(void) +{ + clear_sda(); + set_scl(); + set_sda(); + i2c_delay(); + i2c_started = false; +} + +static void i2c_write_bit(bool bit) +{ + if (bit) + set_sda(); + else + clear_sda(); + i2c_delay(); // ? + set_scl(); + clear_scl(); +} + +static bool i2c_read_bit(void) +{ + bool bit; + + set_sda(); + set_scl(); + bit = read_sda(); + clear_scl(); + + return bit; +} + +bool i2c_write_byte(bool send_start, bool send_stop, uint8_t byte) +{ + uint8_t bit; + bool nack; + + if (send_start) + i2c_start_cond(); + + for (bit = 0; bit < 8; bit++) { + i2c_write_bit((byte & 0x80) != 0); + byte <<= 1; + } + + nack = i2c_read_bit(); + + if (send_stop) + i2c_stop_cond(); + + return nack; +} + +uint8_t i2c_read_byte(bool nack, bool send_stop) +{ + uint8_t byte = 0; + uint8_t bit; + + for (bit = 0; bit < 8; bit++) { + byte = (byte << 1) | i2c_read_bit(); + } + + i2c_write_bit(nack); + + if (send_stop) + i2c_stop_cond(); + + return byte; +} + + +/* EEPROM related code */ + +int eeprom_write_byte(uint8_t slave, uint8_t addr, uint8_t byte) +{ + bool nack; + + /* Write slave address */ + nack = i2c_write_byte(true, false, slave << 1); + if (nack) + goto out_stop; + nack = i2c_write_byte(false, false, addr); + if (nack) + goto out_stop; + nack = i2c_write_byte(false, true, byte); + if (nack) + goto out_stop; + +out_stop: + i2c_stop_cond(); + if (nack) + return -1; + else + return 0; +} + +int eeprom_read_byte(uint8_t slave, uint8_t addr) +{ + bool nack; + + /* dummy write cycle */ + nack = i2c_write_byte(true, false, slave << 1); + if (nack) + goto out_stop; + nack = i2c_write_byte(false, false, addr); + if (nack) + goto out_stop; + /* Re-start with read */ + nack = i2c_write_byte(true, false, (slave << 1) | 1); + if (nack) + goto out_stop; + + return i2c_read_byte(true, true); + +out_stop: + i2c_stop_cond(); + if (nack) + return -1; + else + return 0; +} |