Re: [libopencm3-devel] I2C on STM32L1?

[Chris C. <chr...@gm...>]

Thank you! That helped me get up and running. There were two things I was
missing. First, the call to gpio_set_output_options() with GPIO_OTYPE_OD
appears to be critical; it's not sufficient to put this in
gpio_mode_setup(). Second, with GPIO_OTYPE_OD, apparently I need to
use i2c_set_speed(), instead of i2c_set_clock_frequency() and/or
i2c_set_fast/standard_mode().

After that, my address write received ACK. But I still was not able to use
i2c_send_data(); this apparently did nothing. However, using
i2c_transfer7() as you suggested, worked fine. So I am good for now (albeit
a little confused about the old/low-level interface versus the new one..).

Would it be helpful for me to submit a working L1 I2C example for
libopencm3-examples <https://github.com/libopencm3/libopencm3-examples>?

_chris



On Sun, Aug 2, 2020 at 10:24 AM Karl Palsson <ka...@tw...> wrote:

>
> https://github.com/karlp/libopencm3-tests/tree/master/tests/i2c-master
> is the code I wrote while developing the "standard" api. (You
> shouldn't really have to know about the v1/v2 differences, for
> the most part...) Those "set_fast_mode" and "set_standard_mode"
> are part of the original very low level apis. you (probably) want
> something more like:
>
>
> https://github.com/karlp/libopencm3-tests/blob/master/tests/i2c-master/i2c-master.c#L29-L38
> (i2c_set_speed(
> <https://github.com/karlp/libopencm3-tests/blob/master/tests/i2c-master/i2c-master.c#L29-L38(i2c_set_speed(>)
> and then just i2c_transfer7()
>
> The main-<hardware> have the onnly board specfic setup required,
> normally setting up clocks and gpio modes.
>
> There's a couple of issues reported with i2c as well:
> https://github.com/libopencm3/libopencm3/pulls?q=is%3Apr+is%3Aopen+i2c
> that _may_ be relevant to you, or at least to bear in mind.
>
>
> Chris Chronopoulos <chr...@gm...> wrote:
> > Hmm, well update - I figured out that I was missing the
> > following line:
> >
> >     rcc_periph_clock_enable(RCC_GPIOB);
> >
> > before my GPIO setup calls. Makes sense. The thing I'm confused
> > about now is the clock speed. With i2c_set_fast_mode(), I get a
> > clock speed of 178 kHz. With i2c_set_standard_mode(), it's 266
> > kHz. Weird, shouldn't fast mode be.. faster?
> >
> > Also, one more thing: if I try and wait for "address
> > transferred" by doing:
> >
> >     while (!(I2C_SR1(I2C1) & I2C_SR1_ADDR));
> >
> > after the i2c_send_7bit_address() call, then it gets stuck
> > here. So I think I am still doing something wrong with the
> > setup.
> >
> >
> > On Sat, Aug 1, 2020 at 6:00 PM Chris Chronopoulos <
> > chr...@gm...> wrote:
> >
> > > I've also noticed that if I put in the while-loops to check for status
> > > register updates, e.g.
> > >
> > >         while (!((I2C_SR1(I2C1) & I2C_SR1_SB)
> > >                 & (I2C_SR2(I2C1) & (I2C_SR2_MSL | I2C_SR2_BUSY))));
> > >
> > > Then this just gets stuck, confirming that the start condition is not
> > > being sent.
> > >
> > > On Sat, Aug 1, 2020 at 5:52 PM Chris Chronopoulos <
> > > chr...@gm...> wrote:
> > >
> > >> Hi, just joined this list, not sure what the protocol is.. but I have
> a
> > >> question about getting I2C working on the STM32L1(52RE).
> > >>
> > >> First of all, I see that there are two versions of the I2C API: v1 and
> > >> v2. Can someone explain what the difference is between these? From
> digging
> > >> through the library, I can see that different device families use
> different
> > >> versions, e.g.:
> > >>
> > >>     F0: v2
> > >>     F1: v1
> > >>     F2: v1
> > >>     F3: v2
> > >>     F4: v1
> > >>     F7: v2
> > >>     L0: v2
> > >>     L1: v1
> > >>     L4: v2
> > >>
> > >> So when following code examples, I guess I need to find examples that
> use
> > >> the v1 API. In libopencm3-examples, the only STM32 I2C v1 example I
> could
> > >> find is this one for F1
> > >> <
> https://github.com/libopencm3/libopencm3-examples/tree/master/examples/stm32/f1/other/i2c_stts75_sensor
> >.
> > >> Unfortunately, the i2c_setup() function in this code doesn't compile
> for
> > >> L1, because of some differences between the RCC and GPIO API's
> (namely,
> > >> RCC_AFIO and gpio_set_mode() are not defined for L1). So I made some
> > >> adjustments based on my best guesses, and ended up with this code
> > >> <
> https://gist.github.com/chronopoulos/d34de9b6119d4ec052451d6afaa99e79>,
> > >> which compiles. But, when I monitor the I2C lines with a logic
> analyzer, I
> > >> see nothing. Dead silence.
> > >>
> > >> Am I missing something? Can anyone provide an example of I2C being
> used
> > >> on STM32L1?
> > >>
> > >>
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