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stmhal: Properly handle RTS/CTS flow control for buf/unbuf transfers. 

Fixes issues #1912 and #1913.  UART documentation is also updated.
This commit is contained in:
Peter Hinch 2016-03-25 10:20:12 +00:00 committed by Damien George
parent 3177ef544f
commit 22cbcd55f0
2 changed files with 122 additions and 23 deletions
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91
docs/library/pyb.UART.rst
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@ -40,7 +40,8 @@ using the standard stream methods::
To check if there is anything to be read, use::
uart.any() # returns True if any characters waiting
uart.any() # returns the number of characters waiting
*Note:* The stream functions ``read``, ``write``, etc. are new in MicroPython v1.3.4.
Earlier versions use ``uart.send`` and ``uart.recv``.
@ -66,12 +67,16 @@ Constructors
- ``UART(3)`` is on ``YB``: ``(TX, RX) = (Y9, Y10) = (PB10, PB11)``
- ``UART(2)`` is on: ``(TX, RX) = (X3, X4) = (PA2, PA3)``
The Pyboard Lite supports UART(1), UART(2) and UART(6) only. Pins are as above except:
- ``UART(2)`` is on: ``(TX, RX) = (X1, X2) = (PA2, PA3)``
Methods
-------
.. only:: port_pyboard
.. method:: uart.init(baudrate, bits=8, parity=None, stop=1, \*, timeout=1000, flow=None, timeout_char=0, read_buf_len=64)
.. method:: uart.init(baudrate, bits=8, parity=None, stop=1, \*, timeout=1000, flow=0, timeout_char=0, read_buf_len=64)
Initialise the UART bus with the given parameters:
@ -79,7 +84,7 @@ Methods
- ``bits`` is the number of bits per character, 7, 8 or 9.
- ``parity`` is the parity, ``None``, 0 (even) or 1 (odd).
- ``stop`` is the number of stop bits, 1 or 2.
- ``flow`` sets the flow control type. Can be None, ``UART.RTS``, ``UART.CTS``
- ``flow`` sets the flow control type. Can be 0, ``UART.RTS``, ``UART.CTS``
or ``UART.RTS | UART.CTS``.
- ``timeout`` is the timeout in milliseconds to wait for the first character.
- ``timeout_char`` is the timeout in milliseconds to wait between characters.
@ -103,16 +108,18 @@ Methods
.. method:: uart.any()
Returns the number of characters waiting (may be 0).
Returns the number of bytes waiting (may be 0).
.. method:: uart.writechar(char)
Write a single character on the bus. ``char`` is an integer to write.
Return value: ``None``.
Return value: ``None``. See note below if CTS flow control is used.
.. method:: uart.read([nbytes])
Read characters. If ``nbytes`` is specified then read at most that many bytes.
If ``nbytes`` are available in the buffer, returns immediately, otherwise returns
when sufficient characters arrive or the timeout elapses.
.. only:: port_pyboard
@ -124,9 +131,9 @@ Methods
.. method:: uart.readall()
Read as much data as possible.
Read as much data as possible. Returns after the timeout has elapsed.
Return value: a bytes object or ``None`` on timeout.
Return value: a bytes object or ``None`` if timeout prevents any data being read.
.. method:: uart.readchar()
@ -144,9 +151,11 @@ Methods
.. method:: uart.readline()
Read a line, ending in a newline character.
Read a line, ending in a newline character. If such a line exists, return is
immediate. If the timeout elapses, all available data is returned regardless
of whether a newline exists.
Return value: the line read or ``None`` on timeout.
Return value: the line read or ``None`` on timeout if no data is available.
.. method:: uart.write(buf)
@ -157,7 +166,8 @@ Methods
bytes are used for each character (little endian), and ``buf`` must contain
an even number of bytes.
Return value: number of bytes written or ``None`` on timeout.
Return value: number of bytes written. If a timeout occurs and no bytes
were written returns ``None``.
.. method:: uart.sendbreak()
@ -173,4 +183,63 @@ Constants
.. data:: UART.RTS
.. data:: UART.CTS
to select the flow control type
to select the flow control type.
Flow Control
------------
.. only:: port_pyboard
On Pyboards V1 and V1.1 ``UART(2)`` and ``UART(3)`` support RTS/CTS hardware flow control
using the following pins:
- ``UART(2)`` is on: ``(TX, RX, nRTS, nCTS) = (X3, X4, X2, X1) = (PA2, PA3, PA1, PA0)``
- ``UART(3)`` is on :``(TX, RX, nRTS, nCTS) = (Y9, Y10, Y7, Y6) = (PB10, PB11, PB14, PB13)``
On the Pyboard Lite only ``UART(2)`` supports flow control on these pins:
``(TX, RX, nRTS, nCTS) = (X1, X2, X4, X3) = (PA2, PA3, PA1, PA0)``
In the following paragraphs the term "target" refers to the device connected to
the UART.
When the UART's ``init()`` method is called with ``flow`` set to one or both of
``UART.RTS`` and ``UART.CTS`` the relevant flow control pins are configured.
``nRTS`` is an active low output, ``nCTS`` is an active low input with pullup
enabled. To achieve flow control the Pyboard's ``nCTS`` signal should be connected
to the target's ``nRTS`` and the Pyboard's ``nRTS`` to the target's ``nCTS``.
CTS: target controls Pyboard transmitter
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If CTS flow control is enabled the write behaviour is as follows:
If the Pyboard's ``uart.write(buf)`` method is called, transmission will stall for
any periods when ``nCTS`` is ``False``. This will result in a timeout if the entire
buffer was not transmitted in the timeout period. The method returns the number of
bytes written, enabling the user to write the remainder of the data if required. In
the event of a timeout, a character will remain in the UART pending ``nCTS``. The
number of bytes composing this character will be included in the return value.
If ``uart.writechar()`` is called when ``nCTS`` is ``False`` the method will time
out unless the target asserts ``nCTS`` in time. If it times out ``OSError 116``
will be raised. The character will be transmitted as soon as the target asserts ``nCTS``.
RTS: Pyboard controls target's transmitter
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If RTS flow control is enabled, behaviour is as follows:
If buffered input is used (``read_buf_len`` > 0), incoming characters are buffered.
If the buffer becomes full, the next character to arrive will cause ``nRTS`` to go
``False``: the target should cease transmission. ``nRTS`` will go ``True`` when
characters are read from the buffer.
Note that the ``any()`` method returns the number of bytes in the buffer. Assume a
buffer length of ``N`` bytes. If the buffer becomes full, and another character arrives,
``nRTS`` will be set False, and ``any()`` will return the count ``N``. When
characters are read the additional character will be placed in the buffer and will
be included in the result of a subsequent ``any()`` call.
If buffered input is not used (``read_buf_len`` == 0) the arrival of a character will
cause ``nRTS`` to go ``False`` until the character is read.

52
stmhal/uart.c
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@ -320,6 +320,10 @@ int uart_rx_char(pyb_uart_obj_t *self) {
data = self->read_buf[self->read_buf_tail];
}
self->read_buf_tail = (self->read_buf_tail + 1) % self->read_buf_len;
if (__HAL_UART_GET_FLAG(&self->uart, UART_FLAG_RXNE) != RESET) {
// UART was stalled by flow ctrl: re-enable IRQ now we have room in buffer
__HAL_UART_ENABLE_IT(&self->uart, UART_IT_RXNE);
}
return data;
} else {
// no buffering
@ -347,6 +351,11 @@ STATIC bool uart_tx_wait(pyb_uart_obj_t *self, uint32_t timeout) {
}
STATIC HAL_StatusTypeDef uart_tx_data(pyb_uart_obj_t *self, uint8_t *data, uint16_t len) {
if (self->uart.Init.HwFlowCtl & UART_HWCONTROL_CTS) {
// CTS can hold off transmission for an arbitrarily long time. Apply
// the overall timeout rather than the character timeout.
return HAL_UART_Transmit(&self->uart, data, len, self->timeout);
}
// The timeout specified here is for waiting for the TX data register to
// become empty (ie between chars), as well as for the final char to be
// completely transferred. The default value for timeout_char is long
@ -385,25 +394,25 @@ void uart_irq_handler(mp_uint_t uart_id) {
}
if (__HAL_UART_GET_FLAG(&self->uart, UART_FLAG_RXNE) != RESET) {
#if defined(MCU_SERIES_F7)
int data = self->uart.Instance->RDR; // clears UART_FLAG_RXNE
#else
int data = self->uart.Instance->DR; // clears UART_FLAG_RXNE
#endif
data &= self->char_mask;
if (self->read_buf_len != 0) {
uint16_t next_head = (self->read_buf_head + 1) % self->read_buf_len;
if (next_head != self->read_buf_tail) {
// only store data if room in buf
// only read data if room in buf
#if defined(MCU_SERIES_F7)
int data = self->uart.Instance->RDR; // clears UART_FLAG_RXNE
#else
int data = self->uart.Instance->DR; // clears UART_FLAG_RXNE
#endif
data &= self->char_mask;
if (self->char_width == CHAR_WIDTH_9BIT) {
((uint16_t*)self->read_buf)[self->read_buf_head] = data;
} else {
self->read_buf[self->read_buf_head] = data;
}
self->read_buf_head = next_head;
} else { // No room: leave char in buf, disable interrupt
__HAL_UART_DISABLE_IT(&self->uart, UART_IT_RXNE);
}
} else {
// TODO set flag for buffer overflow
}
}
}
@ -427,6 +436,15 @@ STATIC void pyb_uart_print(const mp_print_t *print, mp_obj_t self_in, mp_print_k
} else {
mp_printf(print, "%u", self->uart.Init.Parity == UART_PARITY_EVEN ? 0 : 1);
}
if (self->uart.Init.HwFlowCtl) {
mp_printf(print, ", flow=");
if (self->uart.Init.HwFlowCtl & UART_HWCONTROL_RTS) {
mp_printf(print, "RTS%s", self->uart.Init.HwFlowCtl & UART_HWCONTROL_CTS ? "|" : "");
}
if (self->uart.Init.HwFlowCtl & UART_HWCONTROL_CTS) {
mp_printf(print, "CTS");
}
}
mp_printf(print, ", stop=%u, timeout=%u, timeout_char=%u, read_buf_len=%u)",
self->uart.Init.StopBits == UART_STOPBITS_1 ? 1 : 2,
self->timeout, self->timeout_char,
@ -434,7 +452,7 @@ STATIC void pyb_uart_print(const mp_print_t *print, mp_obj_t self_in, mp_print_k
}
}
/// \method init(baudrate, bits=8, parity=None, stop=1, *, timeout=1000, timeout_char=0, read_buf_len=64)
/// \method init(baudrate, bits=8, parity=None, stop=1, *, timeout=1000, timeout_char=0, flow=0, read_buf_len=64)
///
/// Initialise the UART bus with the given parameters:
///
@ -444,6 +462,7 @@ STATIC void pyb_uart_print(const mp_print_t *print, mp_obj_t self_in, mp_print_k
/// - `stop` is the number of stop bits, 1 or 2.
/// - `timeout` is the timeout in milliseconds to wait for the first character.
/// - `timeout_char` is the timeout in milliseconds to wait between characters.
/// - `flow` is RTS | CTS where RTS == 256, CTS == 512
/// - `read_buf_len` is the character length of the read buffer (0 to disable).
STATIC mp_obj_t pyb_uart_init_helper(pyb_uart_obj_t *self, mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
static const mp_arg_t allowed_args[] = {
@ -847,7 +866,7 @@ STATIC mp_uint_t pyb_uart_write(mp_obj_t self_in, const void *buf_in, mp_uint_t
return MP_STREAM_ERROR;
}
// wait to be able to write the first character
// wait to be able to write the first character. EAGAIN causes write to return None
if (!uart_tx_wait(self, self->timeout)) {
*errcode = EAGAIN;
return MP_STREAM_ERROR;
@ -859,6 +878,17 @@ STATIC mp_uint_t pyb_uart_write(mp_obj_t self_in, const void *buf_in, mp_uint_t
if (status == HAL_OK) {
// return number of bytes written
return size;
} else if (status == HAL_TIMEOUT) { // UART_WaitOnFlagUntilTimeout() disables RXNE interrupt on timeout
if (self->read_buf_len > 0) {
__HAL_UART_ENABLE_IT(&self->uart, UART_IT_RXNE); // re-enable RXNE
}
// return number of bytes written
if (self->char_width == CHAR_WIDTH_8BIT) {
return size - self->uart.TxXferCount - 1;
} else {
int written = self->uart.TxXferCount * 2;
return size - written - 2;
}
} else {
*errcode = mp_hal_status_to_errno_table[status];
return MP_STREAM_ERROR;