Small Scale Production Automation

Manufacturing needs vary for any company. For larger companies producing large quantities, the problem is often resolved through the use of organizations which specialize in high volume operations. Smaller companies, or first runs of a product, often require localized, engineering centric manufacturing fixtures which can be utilized by floor personal who are not highly trained in engineering. These fixtures are used to accomplish a variety of tasks, such as:

Figure 1 shows an example fixture which helps automate all of these processes.

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Figure 1 ‒ Manufacturing Test/Deployment Fixture

The type configuration shown in Figure 1 is designed to be assembled by engineering staff, but simple enough to use by staff who are not as highly trained. The key aspects of this test fixture are:

  1. A BDI-3000 JTAG Emulator is shown; although these are currently end of life, they are still available from several sources. This simple tool allows interaction with the host processor via a JTAG interface, allowing many operations to be done, such as programming of flash and running of diagnostics. And, there are many alternatives to the BDI-3000 that may be better suited for the processor in use.
  2. A core Python set of classes for not only controlling the BDI-3000, but for interfacing with a UART based console on the target. This set of classes provide primary sequencing and control designed specifically for any operations which are required.
  3. The host test fixture is Linux based, and this provides NFS/TFTP services for the target, such as a NFS Root Filesystem, as well as allowing boot of a Linux Kernel from U-Boot on the Target.
  4. Connected Windows or Linux based clients to the host test fixture are able to run extremely simple Python scripts which cause various actions to happen, such as installing default images in flash, or running diagnostics. These scripts are kept extremely simply, as the complex work is done by the core Python classes on the test fixture. Effectively, they can look like MS-DOS based batch files, and floor personal can be easily trained to modify and/or create simple control scripts.

Operational Flow

For the sake of discussion, two types of operational flow are discussed: First boot installation, and failed board diagnostics (RMA).

First Boot Installation

In this case, it is assumed that the target hardware comes from the board house with blank flash. This is often the case with NAND flash, which has specialized handling characteristics around it due to bad block management. Other cases are where eMMC or NOR flash does have a pre-programed image in it, but often is way out of date. A typical flow would be:

  1. Connect to Manufacturing Fixture, power up.
  2. Execute a script on the client machine which as the simple Python scripting, which invokes the more complex scripting on the test fixture host to initiate flash programing through the BDI-3000. Typically, this would simply install U-Boot or Diagnostics (or a version of U-Boot which contains Diagnostics).
  3. After first installation, reboot and then run Diagnostics, monitoring output and detecting pass/fail conditions. These diagnostics could emit messages on the console, or in more advanced settings (not shown in Figure 1), several LED's could show state, and these LED's, controlled by GPIO's, could also be connected to the Manufacturing Fixture; the GPIO's could be brought out on a stick header, and connected to a parallel port on the test fixture, allowing the core Python classes to monitor state.
  4. If the target passes Diagnostics, additional control scripting could be used to cause U-Boot to load a Linux Kernel via TFTP, mount a Root Filesystem NFS, and do final production flashing and configuration using company specific upgrade/install logic.

Although this is a very simplified example, it does demonstrate how using base Python classes on the Manufacturing Fixture allow connected clients to cause complex operations with simple steps.

Failed Board Diagnostics

Typically for drop-out from manufacturing, or for customer RMA, these operations are very similar to First Boot Installation: Simple control scripts on the connected client to execute complex commands via the Manufacturing Fixture, initiating a variety of diagnostics and monitoring the results. Some examples:

  1. Run a full set of diagnostics from the BDI-3000; this allows the diagnostics to run without any target firmware executing. Thus, if the NAND/NOR has failed, diagnostics can be run on it. The same applies for SDRAM.
  2. Run higher-level complex diagnostics, such as network tests.
  3. Initiate POST which reside in U-Boot.
  4. For high-speed network interfaces, it's often desired to exercise low-level diagnostics at the PHY level, capturing data such as Eye Diagrams. A Manufacturing Fixture of this nature can greatly automate this process.

Summary

Every target configuration, and development house, will have different needs. Yet, these simple approaches can easily simplify day to day operations of designed in at engineering time. As targets are brought-up and application code is developed, the Manufacturing Fixture becomes and extension to the Development Engineering Team, and they can create base Python control classes incrementally, classes which are then easily sequenced by very simple Python scripting on connected clients by technicians.