Merge pull request #42 from brainelectronics/bugfix/use-most-generic-…

…uart-functions

Use most generic UART functions

changelog.md

@@ -15,6 +15,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 <!-- ## [Unreleased] -->
 
 ## Released
+## [2.1.2] - 2022-12-28
+### Changed
+- Baudrate specific inter frame time is used at Modbus RTU internal function `_uart_read` of [serial.py](umodbus/serial.py) instead of constant value of 5ms
+
+### Fixed
+- ESP32 port specific `wait_tx_done` function replaced by generic wait time calculation in `_send` function of [serial.py](umodbus/serial.py), see #34
+- A 1ms delay has been added between turning the RS485 control pin on and sending the Modbus PDU in `_send` function of [serial.py](umodbus/serial.py)
+
 ## [2.1.1] - 2022-12-27
 ### Fixed
 - Removed unnecessary dependency to `micropython-urequests` from Docker files, setup guide and package setup file
@@ -182,8 +190,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - PEP8 style issues on all files of [`lib/uModbus`](lib/uModbus)
 
 <!-- Links -->
-[Unreleased]: https://github.com/brainelectronics/micropython-modbus/compare/2.1.1...develop
+[Unreleased]: https://github.com/brainelectronics/micropython-modbus/compare/2.1.2...develop
 
+[2.1.2]: https://github.com/brainelectronics/micropython-modbus/tree/2.1.2
 [2.1.1]: https://github.com/brainelectronics/micropython-modbus/tree/2.1.1
 [2.1.0]: https://github.com/brainelectronics/micropython-modbus/tree/2.1.0
 [2.0.0]: https://github.com/brainelectronics/micropython-modbus/tree/2.0.0

umodbus/serial.py

@@ -109,6 +109,7 @@ def __init__(self,
         else:
             self._ctrlPin = None
 
+        self._t1char = (1000000 * (data_bits + stop_bits + 2)) // baudrate
         if baudrate <= 19200:
             # 4010us (approx. 4ms) @ 9600 baud
             self._t35chars = (3500000 * (data_bits + stop_bits + 2)) // baudrate
@@ -172,7 +173,9 @@ def _uart_read(self) -> bytearray:
                 # variable length function codes may require multiple reads
                 if self._exit_read(response):
                     break
-            time.sleep(0.05)
+
+            # wait for the maximum time between two frames
+            time.sleep_us(self._t35chars)
 
         return response
 
@@ -245,13 +248,15 @@ def _send(self, modbus_pdu: bytes, slave_addr: int) -> None:
 
         if self._ctrlPin:
             self._ctrlPin(1)
+            time.sleep_us(1000)     # wait until the control pin really changed
+            send_start_time = time.ticks_us()
 
         self._uart.write(serial_pdu)
 
         if self._ctrlPin:
-            while not self._uart.wait_tx_done(2):
+            total_frame_time_us = self._t1char * len(serial_pdu)
+            while time.ticks_us() <= send_start_time + total_frame_time_us:
                 machine.idle()
-            time.sleep_us(self._t35chars)
             self._ctrlPin(0)
 
     def _send_receive(self,