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SI Units

lbuild module: modm:math:units

modm uses a couple of common SI units for configuration of peripherals:

  • frequency_t in Hertz: Hz, kHz and MHz.
  • baudrate_t in Baud: Bd, kBd, MBd.
  • bitrate_t in bit/s, bps.

These are integral units, so 1 Hz/Bd/bps cannot be split further, and are cast directly to uint32_t type, so they can be used as a non-type template argument.

Conversion can be done via constexpr functions from any numerical type:

  • modm::Hz(T value), modm::kHz(T value), modm::MHz(T value).
  • modm::Bd(T value), modm::kBd(T value), modm::MBd(T value).
  • modm::bps(T value), modm::kbps(T value), modm::Mbps(T value).

In addition, user-defined literals are provided in the modm::literals namespace:

using namespace modm::literals;

frequency_t frequency = modm::Mhz(10.5);
            frequency = 10.5_MHz;
baudrate_t baudrate = 115.2_kBd;
           baudrate = modm::kBd(115.2);
bitrate_t bitrate = modm::kbps(125);
          bitrate = 125_kbps;

frequency = 4295_MHz; // OVERFLOW at 2^32 units!


Percentages are stored as normalized floating point numbers and can be converted using these convenience constructors:

using namespace modm::literals;

percent_t tolerance = modm::pct(10);
          tolerance = 10_pct;
          tolerance = 0.1f;


Simplified types allow passing std::chrono::duration values as template parameters:

seconds_t duration = 10s;
milliseconds_t duration = 10ms;
microseconds_t duration = 10us;

auto count = duration.count();

template< milliseconds_t period >
void setPeriod()
    auto seconds = 1000.0 / period.count();


modm:math:units modm_math_units modm: math: units modm_architecture modm: architecture modm_math_units->modm_architecture