time.sleep() is too inaccurate; use microcontroller.delay_us()

Author: dhalbert

lcd/i2c_pcf8574_interface.py

@@ -18,16 +18,14 @@
 # IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 # CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
-import time
+"""Low-level interface to PCF8574."""
 
 import busio
 import board
 from adafruit_bus_device.i2c_device import I2CDevice
 
 from .lcd import LCD_4BITMODE, LCD_BACKLIGHT, LCD_NOBACKLIGHT, PIN_ENABLE
 
-MICROSECOND = 1e-6
-MILLISECOND = 1e-3
 
 class I2CPCF8574Interface:
 
@@ -81,12 +79,14 @@ def _write4bits(self, value):
         """Pulse the `enable` flag to process value."""
         with self.i2c_device:
             self._i2c_write(value & ~PIN_ENABLE)
-            time.sleep(MICROSECOND)
+            # This 1us delay is probably unnecessary, given the time needed
+            # to execute the statements.
+            microcontroller.delay_us(1)
             self._i2c_write(value | PIN_ENABLE)
-            time.sleep(MICROSECOND)
+            microcontroller.delay_us(1)
             self._i2c_write(value & ~PIN_ENABLE)
         # Wait for command to complete.
-        time.sleep(100*MICROSECOND)
+        microcontroller.delay_us(100)
 
     def _i2c_write(self, value):
         self.data_buffer[0] = value