Integrated System Build & Test
Table of Contents
Team Vision for Integrated System Build & Test PhaseThe goal for this phase of the project was to carry out more tests on individual boards, place orders for additional components and finish the layout for final PCB. The tests for the boards are ongoing, the purchase list has been generated and the layout for the final PCB is complete.
Test Results Summary
- USB Audio Subsystem (CM108 Chip) Testing
In the original test at least four electrical short conditions resulted from bridging due to improper soldering. The CM108 chip was resoldered and tested again; this time all basic continuity tests passed except for the right-channel audio output which was shorted to ground. With no power to the chip, audio was successfully passed through from the input pin to the left-channel output pin. However with power applied (5V), the output remained silent even when a signal was input.
At this stage it was also understood that the testing of USB functionality would take precedence over the testing of audio functionality. After connecting the CM108 chip to the Raspberry Pi via a USB cable, an attempt was made to communicate with the CM108 via the Pi's built-in terminal, but this was unsuccessful. After a bit of troubleshooting it was safe to assume that the chip had probably been rendered defective; a fresh chip was soldered to a fresh board, this time with the direct assistance from the manager of RIT's SMT Lab, Jeff Lonneville, to ensure that soldering would not be the weakest link in the process. But even with this new chip, no USB communication could take place. It was suggested that the chip should be supplied with a 12 MHz clock signal, so a trace was cut and an attempt made to feed this signal into the cut trace by means of a soldered wire and clipped connection to a signal generator. However, this method proved too tedious and inefficient; a board redesign would be necessary to facilitate proper testing.
At this point the end of our allotted testing phase had arrived and although the USB Audio board had passed most of its basic continuity tests, functionality of the board under power could not be verified and communication could not be performed. The focus was then directed towards modifying the original circuit schematic, incorporating some extra elements (per suggestion of the data sheet's reference application circuit) such as a 12 MHz crystal to drive the clock and various additional resistors and capacitors. The modified schematic is being incorporated into the final design in which all subsystems are integrated on a single chip.