Excuting the code:
i2c = I2C(1, I2C.CONTROLLER, dma=True)
tmp = i2c.recv(1, i2c_addr)
recv_data = bytearray(56)
i2c.recv(recv_data, i2c_addr)
The second i2c.recv() fails with OSError: [Errno 110] ETIMEDOUT. When
receiving greater than or equal to 2 bytes at first i2c.recv(), the second
i2c.recv() succeeds. This issue does not occur without DMA.
Details of change: when executing I2C with DMA:
- Bit 11 of I2Cx_CR2 (DMA Request Enable) should be 1 to indicate that DMA
transfer is enabled. This bit is set after I2C event interrupt is
enabled in HAL_I2C_Master_Transmit_DMA()/HAL_I2C_Master_Receive_DMA(), so
DMA Request Enable bit might be 0 in IRQHandler.
- In case of data receive:
- When only 1 byte receiption, clear I2Cx_CR1's bit 10 (ACK).
- When only 2 byte receiption, clear I2Cx_CR1's bit 10 (ACK) and set
bit 11 (POS).
- When greater than or equal to 2 byte receiption, bit 12 of I2Cx_CR2
(DMA Last Transfer) should set to generate NACK when DMA transfer
completed.
Otherwise, the I2C bus may be busy after received data from peripheral.
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