Thu 18 April 2019

Codethink engineers develop custom debug solution for customer project

For a project with one of our larger clients, Codethink engineers had been using a 3rd party debugging board, purchased by the customer. Engineers found that the debug board features were quite limited. Due to the delicate design of the board, the lead time for production was long and as a result, supplies were running out. It was clear that an alternative solution was needed. There was a desire to be able to automate the changing of debug settings on the board. Previous boards were using manual switches to change debug and boot modes.

To address the deficiencies of the board used, Codethink engineers, with the trust of the client, developed their own bespoke debugging board. This was created specifically for use for the customer project and their IVI. This was referred to as the ‘Ben Debug Board’ or the ‘Benbug Board’, named after the engineer primarily responsible for development.

Codethink reviewed the initial design of the debugging board and the connections in use in order to understand how the solution worked. Our team then identified improvements that could be made, selecting compatible parts based on data availability and Linux support.

“The initial prototype used a SPI GPIO expander and some small logic to do various debug controls. The second prototype moved to an Atmel ATMega device to provide more IO, a basic command line interface and some programmable reaction to IO changes.

The ATMega was chosen as there was already support for avr-gcc in Debian and it gave us enough code space to do what we wanted.

Having a control system that could be connected to via a serial terminal allowed the customer to use it as their engineers used Windows laptops which did not allow custom driver loading.” - Ben

The board is in use at customer site and Codethink's offices. Further development on a later iteration of the board, with added robustness is ongoing in the background of other work being carried out. The developments allow for reset and boot mode control as well as JTAG access to system logic devices.

The board was initially designed using Eagle. This was used for the first two revisions due to familiarity. Once KiCad v5 was released, using the Eagle import tool, the work was transferred to KiCad. This free and open source software was used for further development and allowed engineers to move to using a four layer board. It also aligns with our objectives to use open source technology wherever possible.

KiCad is a tool which has been trusted in other cases for PCB layout design and schematic capture in work carried out by Codethink engineers.

The overall bill of materials for the Codethink-developed board works out to be cheaper to produce than the original debugging board yet with greater functionality, demonstrating the effectiveness of the creative approach Codethink engineers took to the issue. This approach was enabled by the trust we had earned from the customer.

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