This commit adds support for the `timeout` keyword argument to machine.I2C
on the rp2 port, following how it's done on other ports.
The main motivation here is avoid the interpreter crashing due to infinite
loops when SDA is stuck low, which is quite common if the board gets reset
while reading from an I2C device.
A default timeout of 50ms is chosen because it's consistent with:
- Commit a707fe50b0 which used a timeout of
50,000us for zero-length writes on the rp2 port.
- The machine.SoftI2C class which uses 50,000us as the default timeout.
- The stm32 port's hardware I2C, which uses 50,000us for
I2C_POLL_DEFAULT_TIMEOUT_US.
This commit also fixes the default timeout on the esp32 port to be
consistent with the above, and updates the documentation for machine.I2C to
document this keyword argument.
Prior to this commit, the actual I2C frequency can be faster than specified
one and it may exceed the I2C's specification for Fast Mode. The frequency
of SCL should be less than or equal to 400KHz in Fast Mode.
This commit fixes this issue for F4 MCUs by rounding up the division in the
frequency calculation.
Quite regularly users complain about unexpected behavior of I2C, calling it
a bug, when in fact the trouble is caused by missing pull-up resistors. So
this commit adds a note to the documentation, in the slim hope that people
will find and read it.
Some devices, eg BNO055, can stretch SCL for a long time, so make the
default large to accommodate them. 50ms matches the current default for
stm32 hardware I2C .
Signed-off-by: Damien George <damien@micropython.org>
Latest versions of Sphinx (at least 3.1.0) do not need the `*` escaped and
will render the `\` in the output if it is there, so remove it.
Fixes issue #6209.
This allows to efficiently send to an I2C slave data that is made up of
more than one buffer. Instead of needing to allocate temporary memory to
combine buffers together this new method allows to pass in a tuple or list
of buffers. The name is based on the POSIX function writev() which has
similar intentions and signature.
The reasons for taking this approach (compared to having an interface with
separate start/write/stop methods) are:
- It's a backwards compatible extension.
- It's convenient for the user.
- It's efficient because there is only one Python call, then the C code can
do everything in one go.
- It's efficient on the I2C bus because the implementation can do
everything in one go without pauses between blocks of bytes.
- It should be possible to implement this extension in all ports, for
hardware and software I2C.
Further discussion is found in issue #3482, PR #4020 and PR #4763.
The memory read/write I2C functions now take an optional keyword-only
parameter that specifies the number of bits in the memory address.
Only mem-addrs that are a multiple of 8-bits are supported (otherwise
the behaviour is undefined).
Due to the integer type used for the address, for values larger than 32
bits, only 32 bits of address will be sent, and the rest will be padded
with 0s. Right now no exception is raised when that happens. For values
smaller than 8, no address is sent. Also no exception then.
Tested with a VL6180 sensor, which has 16-bit register addresses.
Due to code refactoring, this patch reduces stmhal and esp8266 builds
by about 50 bytes.
A standard I2C address is 7 bits but addresses 0b0000xxx and 0b1111xxx
are reserved. The scan() method is changed to reflect this, along with
the docs.
Damien George