TMP117 Library for Raspberry Pi Pico SDK

This version is designed as an INTERFACE library for the Raspberry Pi Pico SDK.

Based on the SparkFun TMP117 Arduino Library by Madison Chodikov, this library has been ported to the Raspberry Pi Pico C SDK. While the basics of the original library remain, much has changed in this version. It was developed for personal use with the TMP117 sensor and as an opportunity to learn the Pico SDK.

Test boards

• Raspberry Pi Pico H (RP2040)
• Pimoroni Pico Plus 2 (RP2350)
• SparkFun SEN-15805 (TMP117)

Reference Materials

• Texas Instruments TMP117 High-Accuracy, Low-Power Digital Temperature Sensor
  Datasheet: TMP117 Datasheet
• SparkFun TMP117 Board: SparkFun SEN-15805
• Raspberry Pi Pico Documentation: Pico Documentation
• Raspberry Pi Pico SDK: Pico SDK

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Library Notes

Examples

• 14 Examples are provided, some within the same directory.
• Tested successfully with Pico SDK 2.1.0 for both RP2040 and RP2350 boards.
• Default board file I2C and UART pins are used. Configure the alert interrupt pin in examples if needed.

In the first temperature reading example (temp_result.c), Q notation is introduced to display temperature values without using floating-point math.

Refer to the TI Application Note: How to Read and Interpret Digital Temperature Sensor Output Data:
"Modern sensors, such as the TMP117, offer a full 16 bits of resolution in a Q7 format."

The 16-bit Word of the temp_result register is structured as follows:

• Bit 15: Sign bit Bits [14:7]: Integer bits "Decimal Point" Bits [6:0]: Fractional bits

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Features

1. Defined Types and Enumerations: Many function parameters now use types and enumerations for clarity. See tmp117.h for details.
2. Efficient Register Reads: The read_register function tracks the last pointer register written to. This avoids unnecessary writes to the pointer register.
3. EEPROM Writes: Writes to registers are volatile unless EEPROM programming is used.
4. New Functions and Examples:
   • Raw temperature register read for Q notation display.
   • one-shot mode examples
   • Alert pin usage as a Data Ready interrupt
   • SMBus alert response example.
   • EEPROM programming functions and examples.

Notes for handling flags and one-shot mode

• Reading the configuration register clears the high alert and low alert flags.
• Reading the temperature result or configuration register clears the data ready flag.
• In one-shot mode, ensure the temperature register is not read before the configuration register to avoid prematurely clearing the data ready flag.

Factory defaults and EEPROM

• Factory default: 8 averaged temperature conversions, conversion cycle time 1 second in CC mode.
• See table Table 7-7. Conversion Cycle Time in CC Mode in the datasheet for details.
• Averaging is supported in both continuous and one-shot modes.
  See section 7.3.2 Averaging in the datasheet for details.
• EEPROM Write Limits: Typical lifespan is 50,000 writes (minimum 1,000 writes).
  Consider recording the values of the general-purpose EEPROM before overwriting them.

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I2C Details

• Ensure your I2C board has pullups, or add them, probably in the 2.2k-4.7k ohm range.
• Possible TMP117 I2C addresses: 0x48, 0x49, 0x4A, 0x4B (set via jumpers on the SparkFun board).
  Default address is 0x48 unless changed using the set_address() function.
• Use tmp117_set_instance() to easily change I2C instance instead of using a board file, if desired.

Note: The device requires 1.5 ms to power up before conversions can begin.

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serial interfaces

• Default serial is USB CDC, comment out the below in each CMakeLists.txt to use default UART

# Enable USB output, disable UART output
pico_enable_stdio_usb(set_alert_mode_temp_limits 1)
pico_enable_stdio_uart(set_alert_mode_temp_limits 0)

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File Structure

• /src - Library source and header files.
• /examples - Example applications for testing and demonstration.

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Using with the Raspberry Pico VS Code Extension

• Open the VS Code command pallet, do Git: Clone then enter the url for this repository.
• Then simply open the Pico-TMP117-Library folder from VS Code.
• Use the CMake Tools extension to specify build and run targets.

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Building the examples from bash on Linux

git clone https://github.com/leafy-psx/Pico-TMP117-Library.git
cd Pico-TMP117-Library
mkdir build && cd build
cmake -DPICO_PLATFORM=rp2040 -DPICO_BOARD=pico -DCMAKE_EXPORT_COMPILE_COMMANDS=1 -DCMAKE_BUILD_TYPE=Release ..
make -j$(nproc)

Or navigate to an individual example directory and run make there.

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Acknowledgments

Thank you to Madison Chodikov @ SparkFun Electronics for writing the original SparkFun TMP117 Qwiic Arduino library and board design. Thanks to kilograham and all contributors to the Raspberry Pi Pico SDK.

See LICENSE.txt for licensing details.