diff options
Diffstat (limited to 'i2c.c')
| -rw-r--r-- | i2c.c | 252 |
1 files changed, 252 insertions, 0 deletions
@@ -0,0 +1,252 @@ +#include <stdio.h> +#include <util/twi.h> +#include <avr/interrupt.h> + +#include "i2c.h" + +volatile twReq twr; + +static void twStartRaw () { + /* disable stop, enable interrupt, reset twint, enable start, enable i2c */ + TWCR = (TWCR & ~(1 << TWSTO)) | (1 << TWIE) | (1 << TWINT) | (1 << TWSTA) | (1 << TWEN); +} + +static void twStopRaw () { + /* disable start, enable interrupt, reset twint, enable stop, enable i2c */ + TWCR = (TWCR & ~(1 << TWSTA)) | (1 << TWIE) | (1 << TWINT) | (1 << TWSTO) | (1 << TWEN); +} + +static void twFlushRaw () { + /* disable start/stop, enable interrupt, reset twint, enable i2c */ + TWCR = (TWCR & ~((1 << TWSTA) | (1 << TWSTO) | (1 << TWEA))) | (1 << TWIE) | (1 << TWINT) | (1 << TWEN); +} + +/* flush and send master ack */ +static void twFlushContRaw () { + /* disable start/stop, enable interrupt, reset twint, enable i2c, send master ack */ + TWCR = (TWCR & ~((1 << TWSTA) | (1 << TWSTO))) | (1 << TWIE) | (1 << TWINT) | (1 << TWEN) | (1 << TWEA); +} + +static void twWaitRaw () { + while (!(TWCR & (1 << TWINT))); +} + +static bool twWriteRaw (const uint8_t data) { + TWDR = data; + if (TWCR & (1 << TWWC)) { + printf("write collision\n"); + return false; + } else { + return true; + } +} + +void twInit () { + /* set scl to 3.6 kHz (at 1Mhz CPU speed)*/ + TWBR = 2; + TWSR |= 0x3; /* set prescaler to 64 */ + + twr.mode = TWM_INVALID; + twr.status = TWST_ERR; +} + +/* high-level write + */ +bool twWrite (const uint8_t address, const uint8_t subaddress, + const uint8_t data) { + /* do not start if request is pending */ + if (twr.status == TWST_WAIT) { + return false; + } + + twr.mode = TWM_WRITE; + twr.address = address; + twr.subaddress = subaddress; + twr.data = data; + twr.step = 0; + twr.status = TWST_WAIT; + /* wait for stop finish */ + while (TW_STATUS != 0xf8); + twStartRaw (); + + return true; +} + +/* high-level read for multiple bytes/addresses + */ +bool twReadMulti (const uint8_t address, const uint8_t subaddress, + uint8_t * const retData, const uint8_t count) { + /* do not start if request is pending */ + if (twr.status == TWST_WAIT) { + return false; + } + + twr.mode = TWM_READ_MULTI; + twr.address = address; + twr.subaddress = subaddress; + twr.retData = retData; + twr.count = count; + twr.i = 0; + twr.step = 0; + twr.status = TWST_WAIT; + /* wait for stop finish */ + while (TW_STATUS != 0xf8); + twStartRaw (); + + return true; +} + +/* handle interrupt, write request + */ +static void twIntWrite () { + switch (twr.step) { + case 0: + if (TW_STATUS == TW_START) { + twWriteRaw (twr.address | TW_WRITE); + twFlushRaw (); + } else { + twr.status = TWST_ERR; + } + break; + + case 1: + if (TW_STATUS == TW_MT_SLA_ACK) { + twWriteRaw (twr.subaddress); + twFlushRaw (); + } else { + twr.status = TWST_ERR; + } + break; + + case 2: + if (TW_STATUS == TW_MT_DATA_ACK) { + twWriteRaw (twr.data); + twFlushRaw (); + } else { + twr.status = TWST_ERR; + } + break; + + case 3: + if (TW_STATUS == TW_MT_DATA_ACK) { + twStopRaw (); + twr.status = TWST_OK; + } else { + twr.status = TWST_ERR; + } + break; + + default: + printf ("nope\n"); + break; + } + ++twr.step; +} + +/* handle interrupt, read request + */ +static void twIntReadMulti () { + switch (twr.step) { + case 0: + if (TW_STATUS == TW_START) { + /* write device address */ + twWriteRaw (twr.address | TW_WRITE); + twFlushRaw (); + ++twr.step; + } else { + twr.status = TWST_ERR; + } + break; + + case 1: + if (TW_STATUS == TW_MT_SLA_ACK) { + /* write subaddress, enable auto-increment */ + twWriteRaw ((1 << 7) | twr.subaddress); + twFlushRaw (); + ++twr.step; + } else { + twr.status = TWST_ERR; + } + break; + + case 2: + if (TW_STATUS == TW_MT_DATA_ACK) { + /* send repeated start */ + twStartRaw (); + ++twr.step; + } else { + twr.status = TWST_ERR; + } + break; + + case 3: + if (TW_STATUS == TW_REP_START) { + /* now start the actual read request */ + twWriteRaw (twr.address | TW_READ); + twFlushRaw (); + ++twr.step; + } else { + twr.status = TWST_ERR; + } + break; + + case 4: + if (TW_STATUS == TW_MR_SLA_ACK) { + /* send master ack if next data block is received */ + twFlushContRaw (); + ++twr.step; + } else { + twr.status = TWST_ERR; + } + + case 5: + if (TW_STATUS == TW_MR_DATA_ACK) { + twr.retData[twr.i] = TWDR; + ++twr.i; + if (twr.i < twr.count-1) { + /* read another byte, not the last one */ + twFlushContRaw (); + /* step stays the same */ + } else { + /* read last byte, send master nack */ + twFlushRaw (); + ++twr.step; + } + } else { + twr.status = TWST_ERR; + } + break; + + case 6: + if (TW_STATUS == TW_MR_DATA_NACK) { + /* receive final byte, send stop */ + twr.retData[twr.i] = TWDR; + twStopRaw (); + twr.status = TWST_OK; + } else { + twr.status = TWST_ERR; + } + break; + + default: + printf ("twIntReadMulti: nope\n"); + break; + } +} + +ISR(TWI_vect) { + switch (twr.mode) { + case TWM_WRITE: + twIntWrite (); + break; + + case TWM_READ_MULTI: + twIntReadMulti (); + break; + + default: + printf ("nope\n"); + break; + } +} + |