try to fix submodule

firmware/lib/Arduino-FOC-drivers/src/encoders/stm32pwmsensor/README.md

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+
+# STM32MagneticSensorPWM
+
+STM32 MCU specific PWM sensor class. This class uses the STM32's hardware timers to precisely capture the PWM input signal, and doesn't use interrupts or have MCU overhead.
+
+:warning: this code is not yet well tested.
+
+## Setup
+
+Please use an advanced control or general purpose timer pin on your STM32. Connect the sensor's PWM output to the MCU's input pin. Usually, pull-ups or pull-downs are not needed, but check your sensor's datasheet.
+
+:warning: only tested on 16 bit timers. Code changes may be needed to make it work on 32 but timers. Avoid using TIM2 and TIM5 unless you want to test it.
+
+The sensor needs the values `min_ticks` and `max-ticks` to be configured correctly to convert the PWM input into an angle. These values will depend on the sensor, but also on the MCU's timer clock speed.
+
+To print the current tick value, use:
+
+```
+sensor.getDutyCycleTicks();
+```
+
+By rotating the motor through several full turns while printing the ticks to the screen you will be able to determine the correct values empirically.
+
+## Usage
+
+```
+STM32MagneticSensorPWM sensor = STM32MagneticSensorPWM(PB7, 412, 6917); // sample values, yours will be different
+
+void setup() {
+    ...
+    sensor.init();
+    ...
+}
+```
+
+To use alternate function timers, set the PinName directly:
+
+```
+sensor._pin = PB_7_ALT1;  // manually set a PinName to use alternate timer function
+```
+
+PWM sensor may have a slow update time (not more often than once per PWM-period, e.g. at the PWM frequency):
+
+```
+sensor.min_elapsed_time = 0.001; // 1ms minimum sample time for velocity
+```