def test_pcf8591_loopback_switching_channels():
adc = PCF8591(i2c, FOUR_SINGLE_ENDED)
p1 = adc.single_ended_input(1)
p2 = adc.single_ended_input(2)
for i in xrange(8):
assert p1.value == 0.0
assert p2.value == 1.0
def test_pcf8591_loopback_differential_gnd_to_ain3():
adc = PCF8591(i2c, THREE_DIFFERENTIAL)
cmp_gnd = adc.differential_input(1)
with adc.output as output:
for v in (i / 255.0 for i in xrange(256)):
output.value = v
assert_is_approx(max(-0.5, -v), cmp_gnd.value)
def test_pcf8591_loopback_differential_vref_to_ain3():
adc = PCF8591(i2c, THREE_DIFFERENTIAL)
cmp_vref = adc.differential_input(2)
with adc.output as output:
for v in (i / 255.0 for i in range(256)):
output.value = v
assert_is_approx(min(0.5, 1 - v), cmp_vref.value)
def test_pcf8591_loopback_single_ended():
adc = PCF8591(i2c, FOUR_SINGLE_ENDED)
input = adc.single_ended_input(3)
with adc.output as output:
for v in (i / 255.0 for i in xrange(256)):
output.value = v
assert_is_approx(v, input.value)
def test_can_be_created_with_one_differential_and_two_single_ended_inputs():
adc = PCF8591(i2c, SINGLE_ENDED_AND_DIFFERENTIAL)
assert adc.single_ended_input_count == 2
assert adc.differential_input_count == 1
assert_all_input_pins_report_direction(adc)
def test_can_be_created_with_three_differential_inputs():
adc = PCF8591(i2c, THREE_DIFFERENTIAL)
assert adc.single_ended_input_count == 0
assert adc.differential_input_count == 3
assert_all_input_pins_report_direction(adc)
def test_can_be_created_with_four_single_ended_inputs():
adc = PCF8591(i2c, FOUR_SINGLE_ENDED)
assert adc.single_ended_input_count == 4
assert adc.differential_input_count == 0
assert_all_input_pins_report_direction(adc)
def create_pcf8591(*args, **kwargs):
adc = PCF8591(*args, **kwargs)
i2c.message_precondition = correct_message_for(adc)
return adc
def test_cannot_be_created_with_an_invalid_mode():
with pytest.raises(ValueError):
PCF8591(i2c, 999)