pyMicroloader

A host loader for embedded microprocessors

Revision history

• V1.1, June 3, 2018: Search for serial devices rather than just taking the first one.
• V1.2, Jan 22, 2019: Change design of pyMicroMem slightly to allow multiple loader types
• V2.0, Aug 06, 2021: Debug and fix up the serial loader. It is now slow but working at 57.6K baud
• V2.1, Feb 01, 2022: Port to Python3
• V2.2, Sep 10, 2022: Support added for Texas Instruments, TMS570 MCUs over serial

Concepts

In this context a host loader is a program, like pyMicroloader, running on a PC computer used by a human to load a program from its disk to an embedded microprocessor (MCU).

A flash loader is code running on the embedded microprocessor communicating with the host loader and saving the program into flash memory.

The intent of this host loader it for use with a cross-development environment for embedded microprocessors. This loader is intended to run in the development environment (or similar); I developed it on Linux (Ubuntu 14 and 18) but also tested it on Windows 7, a while ago.

This program expects a flash loader of some sort to run in the microprocessor. It currently has a class that corresponds to the AltusMetrum flash loader and a separate class that corresponds to the AMSAT Golf-Tee serial loader. The most recent addition is a class communicating with a flash loader running in the Texas Instruments TMS570 MCUs using the ymodem serial protocol.

A new class could be written to use (for example) the ST-Link dongle or a built-in ROM loader in a processor. NOTE: For Windows 7, it needs a driver (well really an INF file) from Altus Metrum to recognize the USB loader device when it is plugged into the USB port.

Similarly, there is class to represent an ELF file. A similar class could be written to represent, say, an iHex file.

Usage

  python pyMicroloader.py filename.elf [--serial n [--force]]
   --serial n specifies the serial number of the device. It must be
     specified if the device has not been flashed.  It it is specified
     and it does not match the flashed device S/N, it will not be
     accepted unless you use:
   --force Ignore the serial number currently flashed and use a newly
     specified one.
   --wait  If the boot loader is not available for some reason keep
     retrying
   --usb  Assume the Altus Metrum usb-based boot loader (default)
   --uart Assume the AMSAT Golf serial UART loader
   --ti-uart Use serial loader (ymodem) for Texas Instruments MCUs

Dependencies

This code depends on the pyserial, pyelftools and modem python packages. See further the Installation section below.

Packages and Classes

pyMicroloader.py depends on files:

• pyMicromem.py contains classes as follows: - MemoryPage which represents a page in the microprocessor - Device which represents all of memory in a microprocessor
• pyAltosFlash.py, which represents the boot loader within the device.
• pySimpleElf.py. This package contains the class SimpleElf, which is really a simple wrapper around the pyelftools class ELFFile.

pyAltosFlash.py, pySerialFlash.py and pyTISerialFlash.py all contain the class FlashLdr, which represents the flavor of the loader to be used.

Installation

Works for both Linux and Windows

1. Install Python 3 for your computer or from python.org if it is not already on your system. Choose the latest update. You also have to pay attention to the OS version that you are using in order to choose the right Python.
2. pip install pyserial
3. pip install pyelftools
4. pip install install/modem-1.1-py3-none-any.whl
5. Clone this repository or download and unzip pyMicroloader (no install necessary)

TODO

• Generally fix errors to work more cleanly. In particular:
  • Fix try/except to better deal with cases when files are not found
  • Deal with cases where the elf file contains more data than the processor has memory
• There may be elf sections and segments that I have not dealt with, but which are required by some uProcs
• The AltosLoader class can take an explicit device name to open for the loader.This is not used by the pyMicroloader.py main program. It should be. In fact, both loaders should be able to take an explicit device name.