Difference between revisions of "STM32 Scan I²C bus"
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[[Category:STM32]][[Category:STM32 Development]][[Category:STM32CubeMX]][[Category:STM32CubeIde]][[Category:STM32 HAL]][[Category:I²C]]{{metadesc|How to scan an I2C bus using STM32 HAL}} | [[Category:STM32]][[Category:STM32 Development]][[Category:STM32CubeMX]][[Category:STM32CubeIde]][[Category:STM32 HAL]][[Category:I²C]]{{metadesc|How to scan an I2C bus using STM32 HAL}} | ||
| − | Scanning an [[I2C]] bus using HAL is really simple. First configure [[I²C]] in [[ | + | Scanning an [[I2C]] bus using HAL is really simple. First configure [[I²C]] in [[STM32CubeMX]]: |
[[File:I2c Config.png|400px]] | [[File:I2c Config.png|400px]] | ||
Revision as of 04:24, 4 June 2021
Scanning an I2C bus using HAL is really simple. First configure I²C in STM32CubeMX:
Once the I²C has been configured, scanning the bus for slaves become a simple matter:
// Go through all possible i2c addresses
for (uint8_t i = 0; i < 128; i++) {
if (HAL_I2C_IsDeviceReady(&hi2c1, (uint16_t)(i<<1), 3, 5) == HAL_OK) {
// We got an ack
printf("%2x ", i);
} else {
printf("-- ");
}
if (i > 0 && (i + 1) % 16 == 0) printf("\n");
}
printf("\n");
The HAL_I2C_IsDeviceReady will return HAL_OK if it receives an ACK or an error if not.
Output from above could be:
-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 1e -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 53 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 68 -- -- -- -- -- -- -- -- -- -- -- -- -- -- 77 -- -- -- -- -- -- -- --
Notice that I²C addresses are a bit peculiar.
The address itself is shifted 1 bit left and the last (LSB) bit indicates read or write. So - if looking at the above table:
0x1e = 30 = 0b00011110
0b00011110 << 1 = 60 = 0x3c
So for use with the HAL_I2C commands, shift the address left by one bit. The HAL library will control the read/write bit.