4.8. I2C¶
4.8.1. Introduction¶
I2C module provides an interface to any I2C-bus-compatible device accessible via I2C serial bus. External components attached to I2C bus can serially transmit/receive data to/from the CPU through two-wire interface. Driver supports three types of transfers in I2C master mode
- Read
- Write
- Write followed by read
In addition driver supports following modes of operation:
- I2C_MODE_BLOCKING: By default, driver operates in blocking mode. In blocking mode, a Task’s code execution is blocked until transaction is complete. This ensures only one transaction operates at a given time. Driver supports both interrupt or non-interrupt based blocking modes.
- I2C_MODE_CALLBACK In callback mode, an I2C transaction functions asynchronously, which means that it does not block a Task’s code execution. After an I2C transaction is complete, I2C driver calls a user-provided hook function. Only interrupt based callback is supported.
Note
If I2C peripheral is in reset during a transfer, it can cause the I2C bus to hang. I2C V0 IP (Keystone SoCs) does not have hardware support to recover the I2C bus from hanging, user needs to power cycle the board as a workaround. For I2C V1 IP (AM3/4/5 SoCs), the application can call I2C_control() API and use I2C_CMD_RECOVER_BUS to recover the I2C bus.
Firmware
TI PRU-ICSS cores (Programmable Real-Time Unit Industrial Communication Subsystem) is firmware programmable and can take on various personalities. Processor SDK package includes I2C Firmware support. Refer I2C FW for additional details.
4.8.2. User Interface¶
4.8.2.1. Driver Configuration¶
Board Specific Configuration
All the board specific configurations eg:enabling and pin-mux of I2C pins should be performed before calling any driver APIs.By default Board_Init() API supports all initialization sequence for TI supported EVMs.Refer PDK Board Support for additional details.
Once the board specific configuration is complete driver API I2C_init() can be called to initialize driver
I2C Configuration Structure
I2C_soc.c file binds driver with hardware attributes on the board through I2C_config structure. This structure must be provided to I2C driver. It must be initialized before the I2C_init() function is called and cannot be changed afterwards.
For details about individual fields of this library structure, see the PDK doxygen documentation
4.8.2.2. APIs¶
API reference for application:
#include <ti/drv/i2c/I2C.h>
Sample code for initiating I2C transaction:
...
Board_init(boardCfg);
...
I2C_socGetInitCfg(peripheralNum, &i2c_cfg);
...
I2C_socSetInitCfg(peripheralNum, &i2c_cfg);
...
i2c = I2C_open(peripheralNum, &i2cParams);
...
...
/* Initiate I2C transfers. Refer Example for details
*/
I2C_transactionInit(&i2cTransaction);
transaction.masterMode = true;
...
...
transferOK = I2C_transfer(i2c, &i2cTransaction);
if (transferOK != I2C_STS_SUCCESS) {
/* I2C transaction failed */
}
4.8.3. Application¶
4.8.3.1. Examples¶
Refer Release Note for I2C support across different EVMs
Name
|
Description
|
Expected Results
|
SoC Supported | Build Type |
|---|---|---|---|---|
| I2C_EepromRead Example application | Simple example to
read fixed number
of bytes from
EEPROM on board and
compares it with
expected data.
|
Following prints will
come on console based
on pass/fail
criteria:
Pass criteria:
EEPROM data matched
All tests have
passed.
|
AM335x, AM437x, AM571x, AM572x, AM574x, k2g, k2hk,k2l,k2e,k2l c6657,c6678 omapl137, | CCS project |
| I2C_Eeprom_Test Application | Simple example to
read fixed number
of bytes from
EEPROM on board and
compares it with
expected data.
|
Following prints will
come on console based
on pass/fail
criteria:
Pass criteria:
I2C bit rate test in
interrupt mode
have passed
I2C probe bus freq
test in interrupt
mode have passed
I2C timeout test in
interrupt mode
have passed
All tests have
passed.
|
am65xx j721e j7200 am64x | makefile |
| I2C_TestApplication | Driver Unit Test
application for
additional I2C
speed and other tests
|
Following prints will
come on console based
on pass/fail
criteria:
Pass criteria:
I2C Test: 100Kbps:
PASS
I2C Test: 400Kbps:
PASS
I2C Test: timeout
test passed
All tests have
passed.
|
AM335x, AM437x, AM571x, AM572x, AM574x, k2g, k2hk, k2l, k2e, c6657, c6678, omapl137, | CCS project |
| am65xx j721e j7200 | makefile | |||
| I2C_SMP_Test Application | Driver Unit Test
application for
additional I2C
speed and other tests
with SMP enabled.
(A15 and A53 cores)
|
Following prints will
come on console based
on pass/fail
criteria:
Pass criteria:
I2C Test: 100Kbps:
PASS
I2C Test: 400Kbps:
PASS
I2C Test: timeout
test passed
All tests have
passed.
|
am572x-evm | CCS project |
| am65xx j721e | makefile | |||
| I2C_TemperatureSensor | Example to get the
temperature value
from the temperature
sensor and displays
on the serial
console.
|
Following prints will
come on console based
on pass/fail
criteria:
Pass criteria:
Temperature =
“value in
centigrades” C
All tests have
passed.
|
AM572x, | CCS project |
| I2C_master/slave | Application
demonstrates
master/slave
transfer of I2C.
Application use
case requires two
EVMs. One acts as
Master and the
other as slave. I2C
connections
information and
addtional details
are as follows:
AM57xx boards I2C bus
connection on J9
(master board <–>
slave board)
pin22 (SCL)<–>
pin22 (SCL)
pin24 (SDA)<–> pin24
(SDA)
pin21 (GND)<–> pin21
(GND)
K2G boards I2C bus
connection on J12
(master board <–>
slave board)
pin28 (SCL)<–>
pin28 (SCL)
pin30 (SDA)<–>
pin30 (SDA)
pin50 (GND)<–>
pin50 (GND)
OMAPL138/C6748
boards I2C bus
connection on J15
(master board <–>
slave board)
pin13 (SCL)<–>
pin13 (SCL)
pin15 (SDA)<–>
pin15 (SDA)
pin35 (GND)<–>
pin35 (GND)
Run
“I2C_Slave_<BoardTy
pe>_<arm/c66x/m4>Test
Project”
first on Slave EVM
and then
“I2C_Master_<BoardT
ype>_<arm/c66x/m4>Tes
tProject”
on Master EVM.
|
Following prints will
come on console based
on pass/fail
criteria:
Pass criteria:
All tests have
passed.
|
AM572x, AM574x, k2g, omapl138, | CCS project |
| tpr12 | makefile |
Note
I2C_Test Application supports write test on Keystone II EVMs, by default write test is disabled, user can enable the write test by defining I2C_EEPROM_WRITE_ENABLE in test/eeprom_read/src/I2C_board.h. I2C_TemperatureSensor Application is supported only on AM572x GP EVM.