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diff --git a/docs/library/pyb.ADC.rst b/docs/library/pyb.ADC.rst deleted file mode 100644 index 51021fdc1..000000000 --- a/docs/library/pyb.ADC.rst +++ /dev/null @@ -1,143 +0,0 @@ -.. currentmodule:: pyb -.. _pyb.ADC: - -class ADC -- analog to digital conversion -========================================= - -.. only:: port_pyboard - - Usage:: - - import pyb - - adc = pyb.ADC(pin) # create an analog object from a pin - val = adc.read() # read an analog value - - adc = pyb.ADCAll(resolution) # create an ADCAll object - val = adc.read_channel(channel) # read the given channel - val = adc.read_core_temp() # read MCU temperature - val = adc.read_core_vbat() # read MCU VBAT - val = adc.read_core_vref() # read MCU VREF - - -Constructors ------------- - - -.. only:: port_pyboard - - .. class:: pyb.ADC(pin) - - Create an ADC object associated with the given pin. - This allows you to then read analog values on that pin. - -Methods -------- - -.. only:: port_pyboard - - .. method:: ADC.read() - - Read the value on the analog pin and return it. The returned value - will be between 0 and 4095. - - .. method:: ADC.read_timed(buf, timer) - - Read analog values into ``buf`` at a rate set by the ``timer`` object. - - ``buf`` can be bytearray or array.array for example. The ADC values have - 12-bit resolution and are stored directly into ``buf`` if its element size is - 16 bits or greater. If ``buf`` has only 8-bit elements (eg a bytearray) then - the sample resolution will be reduced to 8 bits. - - ``timer`` should be a Timer object, and a sample is read each time the timer - triggers. The timer must already be initialised and running at the desired - sampling frequency. - - To support previous behaviour of this function, ``timer`` can also be an - integer which specifies the frequency (in Hz) to sample at. In this case - Timer(6) will be automatically configured to run at the given frequency. - - Example using a Timer object (preferred way):: - - adc = pyb.ADC(pyb.Pin.board.X19) # create an ADC on pin X19 - tim = pyb.Timer(6, freq=10) # create a timer running at 10Hz - buf = bytearray(100) # creat a buffer to store the samples - adc.read_timed(buf, tim) # sample 100 values, taking 10s - - Example using an integer for the frequency:: - - adc = pyb.ADC(pyb.Pin.board.X19) # create an ADC on pin X19 - buf = bytearray(100) # create a buffer of 100 bytes - adc.read_timed(buf, 10) # read analog values into buf at 10Hz - # this will take 10 seconds to finish - for val in buf: # loop over all values - print(val) # print the value out - - This function does not allocate any memory. - -The ADCAll Object ------------------ - -.. only:: port_pyboard - - Instantiating this changes all ADC pins to analog inputs. The raw MCU temperature, - VREF and VBAT data can be accessed on ADC channels 16, 17 and 18 respectively. - Appropriate scaling will need to be applied. The temperature sensor on the chip - has poor absolute accuracy and is suitable only for detecting temperature changes. - - The ``ADCAll`` ``read_core_vbat()`` and ``read_core_vref()`` methods read - the backup battery voltage and the (1.21V nominal) reference voltage using the - 3.3V supply as a reference. Assuming the ``ADCAll`` object has been Instantiated with - ``adc = pyb.ADCAll(12)`` the 3.3V supply voltage may be calculated: - - ``v33 = 3.3 * 1.21 / adc.read_core_vref()`` - - If the 3.3V supply is correct the value of ``adc.read_core_vbat()`` will be - valid. If the supply voltage can drop below 3.3V, for example in in battery - powered systems with a discharging battery, the regulator will fail to preserve - the 3.3V supply resulting in an incorrect reading. To produce a value which will - remain valid under these circumstances use the following: - - ``vback = adc.read_core_vbat() * 1.21 / adc.read_core_vref()`` - - It is possible to access these values without incurring the side effects of ``ADCAll``:: - - def adcread(chan): # 16 temp 17 vbat 18 vref - assert chan >= 16 and chan <= 18, 'Invalid ADC channel' - start = pyb.millis() - timeout = 100 - stm.mem32[stm.RCC + stm.RCC_APB2ENR] |= 0x100 # enable ADC1 clock.0x4100 - stm.mem32[stm.ADC1 + stm.ADC_CR2] = 1 # Turn on ADC - stm.mem32[stm.ADC1 + stm.ADC_CR1] = 0 # 12 bit - if chan == 17: - stm.mem32[stm.ADC1 + stm.ADC_SMPR1] = 0x200000 # 15 cycles - stm.mem32[stm.ADC + 4] = 1 << 23 - elif chan == 18: - stm.mem32[stm.ADC1 + stm.ADC_SMPR1] = 0x1000000 - stm.mem32[stm.ADC + 4] = 0xc00000 - else: - stm.mem32[stm.ADC1 + stm.ADC_SMPR1] = 0x40000 - stm.mem32[stm.ADC + 4] = 1 << 23 - stm.mem32[stm.ADC1 + stm.ADC_SQR3] = chan - stm.mem32[stm.ADC1 + stm.ADC_CR2] = 1 | (1 << 30) | (1 << 10) # start conversion - while not stm.mem32[stm.ADC1 + stm.ADC_SR] & 2: # wait for EOC - if pyb.elapsed_millis(start) > timeout: - raise OSError('ADC timout') - data = stm.mem32[stm.ADC1 + stm.ADC_DR] # clear down EOC - stm.mem32[stm.ADC1 + stm.ADC_CR2] = 0 # Turn off ADC - return data - - def v33(): - return 4096 * 1.21 / adcread(17) - - def vbat(): - return 1.21 * 2 * adcread(18) / adcread(17) # 2:1 divider on Vbat channel - - def vref(): - return 3.3 * adcread(17) / 4096 - - def temperature(): - return 25 + 400 * (3.3 * adcread(16) / 4096 - 0.76) - -
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