improve performance 16 pins interface (#24)

- optimize performance 16 bit interface
  - add readReg16() + writeReg16()
  - based upon ideas from Alex Uta (PR #23)
- update performance test sketch (multi speeds in one run)
- update readme.md
- minor edits

CHANGELOG.md

@@ -6,8 +6,16 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 
-## [0.2.5] - 2023-07-31
+## [0.2.6] - 2023-08-15
+- optimize 16 bit interface
+  - add readReg16() + writeReg16()
+  - based upon ideas from Alex Uta (PR #23)
+- update performance test sketch (multi speeds in one run)
+- update readme.md
+- minor edits
 
+
+## [0.2.5] - 2023-08-14
 - add ESP32 HSPI / VSPI support (Kudo's to Alex Uta, PR #22)
   - add **performance_0.2.4.md** for ESP32
 - add example **MCP23S17_two_SELECT.ino** (#19)
@@ -18,51 +26,41 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - update readme.md
 - minor edits
 
-
 ## [0.2.4] - 2023-02-04
-
 - update readme.md
 - update GitHub actions
 - update license 2023
 
 ## [0.2.3] - 2022-10-20
-
 - add CHANGELOG.md
 - add **enableControlRegister(uint8_t mask)**
 - add **disableControlRegister(uint8_t mask)**
 - add mcp23S17_registers.h  )moved register defines in one place.
 
 ## [0.2.2] - 2022-09-28
-
 - optimize digitalWrite - most used one only.
 
 ## [0.2.1] - 2022-06-29
-
 - add SPIClass as parameter for constructor (See #10)
 - redo constructors.
 - add getAddress() + optimized (_address << 1)
 - update readme.md
 
 ## [0.2.0] - 2022-06-28
-
 - fix #10 incorrect mask
 
 ----
 
 ## [0.1.3] - 2022-04-13
-
 - fix compiling for NANO33 BLE
 
 ## [0.1.2] - 2022-01-12
-
 - change the URL for library manager
 
 ## [0.1.1] - 2022-01-10
-
 - add 16 bit interface
 
 ## [0.1.0] - 2021-12-30
-
 - initial version (a 2019 version did not make it)
 
 

MCP23S17.cpp

@@ -1,7 +1,7 @@
 //
 //    FILE: MCP23S17.cpp
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.2.5
+// VERSION: 0.2.6
 // PURPOSE: Arduino library for SPI MCP23S17 16 channel port expander
 //    DATE: 2021-12-30
 //     URL: https://github.com/RobTillaart/MCP23S17
@@ -359,7 +359,6 @@ void MCP23S17::setSPIspeed(uint32_t speed)
 };
 
 
-
 ///////////////////////////////////////////////////////////////////
 //
 //  8 pins interface
@@ -489,8 +488,7 @@ bool MCP23S17::getPullup8(uint8_t port, uint8_t &mask)
 //  value = 0x0000..0xFFFF bit pattern
 bool MCP23S17::pinMode16(uint16_t value)
 {
-  writeReg(MCP23S17_DDR_A, value >> 8);
-  writeReg(MCP23S17_DDR_B, value & 0xFF);
+  writeReg16(MCP23S17_DDR_A, value);
   _error = MCP23S17_OK;
   return true;
 }
@@ -499,8 +497,7 @@ bool MCP23S17::pinMode16(uint16_t value)
 //  value = 0x0000..0xFFFF   bit pattern
 bool MCP23S17::write16(uint16_t value)
 {
-  writeReg(MCP23S17_GPIO_A, value >> 8);
-  writeReg(MCP23S17_GPIO_B, value & 0xFF);
+  writeReg16(MCP23S17_GPIO_A, value);
   _error = MCP23S17_OK;
   return true;
 }
@@ -510,18 +507,15 @@ bool MCP23S17::write16(uint16_t value)
 uint16_t MCP23S17::read16()
 {
   _error = MCP23S17_OK;
-  uint16_t value = readReg(MCP23S17_GPIO_A);
-  value <<= 8;
-  value += readReg(MCP23S17_GPIO_B);
+  uint16_t value = readReg16(MCP23S17_GPIO_A);
   return value;
 }
 
 
 //  mask = 0x0000..0xFFFF  bit pattern
 bool MCP23S17::setPolarity16(uint16_t mask)
 {
-  writeReg(MCP23S17_POL_A, mask >> 8);
-  writeReg(MCP23S17_POL_B, mask & 0xFF);
+  writeReg16(MCP23S17_POL_A, mask);
   if (_error != MCP23S17_OK)
   {
     return false;
@@ -533,9 +527,7 @@ bool MCP23S17::setPolarity16(uint16_t mask)
 //  mask = 0x0000..0xFFFF  bit pattern
 bool MCP23S17::getPolarity16(uint16_t &mask)
 {
-  mask = readReg(MCP23S17_POL_A);
-  mask <<= 8;
-  mask += readReg(MCP23S17_POL_B);
+  mask = readReg16(MCP23S17_POL_A);
   if (_error != MCP23S17_OK)
   {
     return false;
@@ -547,8 +539,7 @@ bool MCP23S17::getPolarity16(uint16_t &mask)
 //  mask = 0x0000..0xFFFF  bit pattern
 bool MCP23S17::setPullup16(uint16_t mask)
 {
-  writeReg(MCP23S17_PUR_A, mask >> 8);
-  writeReg(MCP23S17_PUR_B, mask & 0xFF);
+  writeReg16(MCP23S17_PUR_A, mask);
   if (_error != MCP23S17_OK)
   {
     return false;
@@ -560,9 +551,7 @@ bool MCP23S17::setPullup16(uint16_t mask)
 //  mask = 0x0000..0xFFFF  bit pattern
 bool MCP23S17::getPullup16(uint16_t &mask)
 {
-  mask = readReg(MCP23S17_PUR_A);
-  mask <<= 8;
-  mask += readReg(MCP23S17_PUR_B);
+  mask = readReg16(MCP23S17_PUR_A);
   if (_error != MCP23S17_OK)
   {
     return false;
@@ -727,6 +716,96 @@ uint8_t MCP23S17::readReg(uint8_t reg)
 }
 
 
+//  writes HIGH byte first, LOW byte last
+bool MCP23S17::writeReg16(uint8_t reg, uint16_t value)
+{
+  _error = MCP23S17_OK;
+
+  if (reg > MCP23S17_OLAT_B)
+  {
+    _error = MCP23S17_REGISTER_ERROR;
+    return false;
+  }
+  ::digitalWrite(_select, LOW);
+  if (_hwSPI)
+  {
+    _mySPI->beginTransaction(_spi_settings);
+    //  _address already shifted
+    _mySPI->transfer(MCP23S17_WRITE_REG | _address );
+    _mySPI->transfer(reg);
+    _mySPI->transfer(value >> 8);
+    ::digitalWrite(_select, HIGH);
+
+    ::digitalWrite(_select, LOW);
+    _mySPI->transfer(MCP23S17_WRITE_REG | _address );
+    _mySPI->transfer(reg + 1);
+    _mySPI->transfer(value & 0xFF);
+    _mySPI->endTransaction();
+  }
+  else
+  {
+    //  _address already shifted
+    swSPI_transfer(MCP23S17_WRITE_REG | _address );
+    swSPI_transfer(reg);
+    swSPI_transfer(value >> 8);
+    ::digitalWrite(_select, HIGH);
+
+    ::digitalWrite(_select, LOW);
+    swSPI_transfer(MCP23S17_WRITE_REG | _address );
+    swSPI_transfer(reg + 1);
+    swSPI_transfer(value & 0xFF);
+  }
+  ::digitalWrite(_select, HIGH);
+  return true;
+}
+
+
+uint16_t MCP23S17::readReg16(uint8_t reg)
+{
+  uint16_t rv = 0;
+
+  _error = MCP23S17_OK;
+
+  if (reg > MCP23S17_OLAT_B)
+  {
+    _error = MCP23S17_REGISTER_ERROR;
+    return false;
+  }
+
+  ::digitalWrite(_select, LOW);
+  if (_hwSPI)
+  {
+    _mySPI->beginTransaction(_spi_settings);
+    //  _address already shifted
+    _mySPI->transfer(MCP23S17_READ_REG | _address );
+    _mySPI->transfer(reg);
+    rv = _mySPI->transfer(0xFF) << 8;
+    ::digitalWrite(_select, HIGH);
+
+    ::digitalWrite(_select, LOW);
+    _mySPI->transfer(MCP23S17_READ_REG | _address );
+    _mySPI->transfer(reg + 1);
+    rv += _mySPI->transfer(0xFF);
+    _mySPI->endTransaction();
+  }
+  else
+  {
+    //  _address already shifted
+    swSPI_transfer(MCP23S17_READ_REG | _address );
+    swSPI_transfer(reg);
+    rv = swSPI_transfer(0xFF) << 8;
+    ::digitalWrite(_select, HIGH);
+
+    ::digitalWrite(_select, LOW);
+    swSPI_transfer(MCP23S17_READ_REG | _address );
+    swSPI_transfer(reg + 1);
+    rv += swSPI_transfer(0xFF);
+  }
+  ::digitalWrite(_select, HIGH);
+  return rv;
+}
+
+
 uint8_t  MCP23S17::swSPI_transfer(uint8_t val)
 {
   uint8_t clk = _clock;

MCP23S17.h

@@ -2,7 +2,7 @@
 //
 //    FILE: MCP23S17.h
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.2.5
+// VERSION: 0.2.6
 // PURPOSE: Arduino library for SPI MCP23S17 16 channel port expander
 //    DATE: 2021-12-30
 //     URL: https://github.com/RobTillaart/MCP23S17
@@ -13,7 +13,7 @@
 #include "MCP23S17_registers.h"
 
 
-#define MCP23S17_LIB_VERSION              (F("0.2.5"))
+#define MCP23S17_LIB_VERSION              (F("0.2.6"))
 
 //  ERROR CODES
 #define MCP23S17_OK                       0x00
@@ -115,6 +115,8 @@ class MCP23S17
   //       USE WITH CARE !!!
   bool     writeReg(uint8_t reg, uint8_t value);
   uint8_t  readReg(uint8_t reg);
+  bool     writeReg16(uint8_t reg, uint16_t value);
+  uint16_t readReg16(uint8_t reg);
 
 
   uint8_t  _address = 0;

README.md

@@ -127,6 +127,9 @@ Returns true if successful.
 - **bool getPullup16(uint16_t &mask)** reads pull-up for 16 channels.
 Returns true if successful.
 
+Since 0.2.6 the reading and writing to registers have been performance optimized for the 16 bit interface.
+If there are problems please open an issue.
+
 
 ### IO Control Register
 

examples/MCP23S17_performance/MCP23S17_performance.ino

@@ -34,11 +34,27 @@ void setup()
   Serial.print("HWSPI: ");
   Serial.println(MCP.usesHWSPI());
 
-  MCP.setSPIspeed(10000000);
+  MCP.setSPIspeed(1000000);
+  test();
+  MCP.setSPIspeed(2000000);
+  test();
+  MCP.setSPIspeed(4000000);
+  test();
+  MCP.setSPIspeed(8000000);
+  test();
 
+  Serial.println("\ndone...");
+}
+
+
+void test()
+{
   MCP.pinMode8(0, 0x00);  //  0 = output , 1 = input
   MCP.pinMode8(1, 0x00);
 
+  Serial.print("\nSPISpeed:\t");
+  Serial.println(MCP.getSPIspeed());
+
   Serial.println("\ntime in microseconds\n");
   delay(100);
 
@@ -127,8 +143,6 @@ void setup()
   Serial.println(val8);
   Serial.print("VAL16:\t");
   Serial.println(val16);
-
-  Serial.println("\ndone...");
 }
 
 

library.json

@@ -15,7 +15,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/MCP23S17.git"
   },
-  "version": "0.2.5",
+  "version": "0.2.6",
   "license": "MIT",
   "frameworks": "arduino",
   "platforms": "*",

library.properties

@@ -1,5 +1,5 @@
 name=MCP23S17
-version=0.2.5
+version=0.2.6
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Arduino library for SPI MCP23S17 16 channel port expander 16 IO-lines