From cbbfe2b4d15c8317d7e4196b9080d240f66ef25a Mon Sep 17 00:00:00 2001
From: Terraneo Federico <fede.tft@miosix.org>
Date: Sun, 5 Jan 2025 15:25:37 +0100
Subject: [PATCH] Activate pullup on serial port RX pin to prevent spurious
received characters on unconnected ports
---
miosix/arch/common/drivers/stm32_serial_common.cpp | 5 +++--
miosix/arch/common/drivers/stm32_serial_common.h | 7 ++++---
miosix/arch/common/drivers/stm32f1_f2_f4_serial.cpp | 5 +++--
miosix/arch/common/drivers/stm32f7_serial.cpp | 2 +-
4 files changed, 11 insertions(+), 8 deletions(-)
diff --git a/miosix/arch/common/drivers/stm32_serial_common.cpp b/miosix/arch/common/drivers/stm32_serial_common.cpp
index 79cea066..64fa397a 100644
--- a/miosix/arch/common/drivers/stm32_serial_common.cpp
+++ b/miosix/arch/common/drivers/stm32_serial_common.cpp
@@ -31,11 +31,12 @@ using namespace miosix;
#if defined(ALTFUNC_STM32F2_SPLIT)
-void STM32SerialAltFunc::set(GpioPin& pin) const
+void STM32SerialAltFunc::set(GpioPin& pin, bool pullUp) const
{
//First we set the AF then the mode to avoid glitches
pin.alternateFunction(lookup(pin));
- pin.mode(Mode::ALTERNATE);
+ if(pullUp) pin.mode(Mode::ALTERNATE_PULL_UP);
+ else pin.mode(Mode::ALTERNATE);
}
inline unsigned char STM32SerialAltFunc::lookup(GpioPin& gpio) const
diff --git a/miosix/arch/common/drivers/stm32_serial_common.h b/miosix/arch/common/drivers/stm32_serial_common.h
index bede0933..7174c9ba 100644
--- a/miosix/arch/common/drivers/stm32_serial_common.h
+++ b/miosix/arch/common/drivers/stm32_serial_common.h
@@ -242,11 +242,12 @@ struct STM32SerialAltFunc
struct STM32SerialAltFunc
{
- void set(GpioPin& pin) const
+ void set(GpioPin& pin, bool pullUp=false) const
{
//First we set the AF then the mode to avoid glitches
pin.alternateFunction(af);
- pin.mode(Mode::ALTERNATE);
+ if(pullUp) pin.mode(Mode::ALTERNATE_PULL_UP);
+ else pin.mode(Mode::ALTERNATE);
}
unsigned char af;
};
@@ -278,7 +279,7 @@ struct STM32SerialAltFunc
};
const Span *spans;
- void set(GpioPin& pin) const;
+ void set(GpioPin& pin, bool pullUp=false) const;
private:
inline unsigned char lookup(GpioPin& gpio) const;
};
diff --git a/miosix/arch/common/drivers/stm32f1_f2_f4_serial.cpp b/miosix/arch/common/drivers/stm32f1_f2_f4_serial.cpp
index 13d352c8..1e6eca5f 100644
--- a/miosix/arch/common/drivers/stm32f1_f2_f4_serial.cpp
+++ b/miosix/arch/common/drivers/stm32f1_f2_f4_serial.cpp
@@ -256,7 +256,8 @@ void STM32SerialBase::commonInit(int id, int baudrate, GpioPin tx, GpioPin rx,
//Quirk: stm32f1 rx pin has to be in input mode, while stm32f2 and up
//want it in ALTERNATE mode. Go figure...
tx.mode(Mode::ALTERNATE);
- rx.mode(Mode::INPUT);
+ rx.mode(Mode::INPUT_PULL_UP_DOWN);
+ rx.pullup(); //Pullup: prevent spurious rx if unconnected
if(flowControl)
{
rts.mode(Mode::ALTERNATE);
@@ -264,7 +265,7 @@ void STM32SerialBase::commonInit(int id, int baudrate, GpioPin tx, GpioPin rx,
}
#else
port->getAltFunc().set(tx);
- port->getAltFunc().set(rx);
+ port->getAltFunc().set(rx,true); //Pullup: prevent spurious rx if unconnected
if(flowControl)
{
port->getAltFunc().set(rts);
diff --git a/miosix/arch/common/drivers/stm32f7_serial.cpp b/miosix/arch/common/drivers/stm32f7_serial.cpp
index 812eb3ee..f417427e 100644
--- a/miosix/arch/common/drivers/stm32f7_serial.cpp
+++ b/miosix/arch/common/drivers/stm32f7_serial.cpp
@@ -428,7 +428,7 @@ void STM32SerialBase::commonInit(int id, int baudrate, GpioPin tx, GpioPin rx,
GpioPin rts, GpioPin cts)
{
port->getAltFunc().set(tx);
- port->getAltFunc().set(rx);
+ port->getAltFunc().set(rx,true); //Pullup: prevent spurious rx if unconnected
if(flowControl)
{
port->getAltFunc().set(rts);
--
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