DACQ and CBOB Detailed Design
Table of Contents
DACQ and CBOB Detailed Design
DACQ Block Diagram
The purpose of the Data Acquisition Board (DACQ) is to be a central point for all data regarding the platform of the SF1 to come to and be saved. This data can be communicated out to the communications board. The DACQ also acquires data from the power monitoring board (PMB) over a SPI connection. A block diagram of the board is show below.
CBOB Block Diagram
The purpose of the Cluster Breakout Board (CBOB) is to act as a master for a grouping of four BioCells. Doing this allows for much less work to be done inside the cells themselves, which is necessary given their limited size of the boards. The CBOB takes data and images over SPI from the cells and stores it onto its micro-SD card using the Pocket Beagle. These images and data can be sent to the Comms board over a separate SPI network. The board itself also regulates 3.3V for each cell, with a maximum power of 3.3W. The current to each cell is monitored and relayed back to the Pocket Beagle over I2C. The board also has a temperature sensor on it. This can all be seen below in the CBOB block diagram.
Schematic Changes from Preliminary Design Review
Some new circuits have been added to both schematics. The DACQ has a new connector for an external microphone from a previous RA of Dr. Patru. The previous MEMs microphone won't be removed. A SPI fanout has been added due to the potential for long connections between boards. Minor changes have also been made to the DACQ throughout review phases. The new DACQ schematics can be seen below.
The CBOB went through much more significant changes. Each cell now requires 5V at 2.5W due to some of the LEDs they need to work with. This decreases the power on the 3.3V line to 0.8W. The 5V converter currently on the CBOB is sufficient to supply the power to 4 different cells and power itself, so no additional 5V converters are made. The 5V line is now divided through current sense resistors and sent to the cells. The 3.3V converters are replaced with integrated modules to decrease the footprint of the board. These converters have all switched and the inductor internal to the part. SPI fanouts have also been added to this board. Minor changes were also made after various design reviews. The schematics can be seen below.
The layout of the CBOB has been completed. The majority of this phase was spent laying out this board, along with the DACQ. The layout needed to be 4 layers due to the power distribution and large number of data channels. The board is 4"x4". The layout of the CBOB can be seen below. Layer 1 is a signaling layer. Layer 2 is a power layer. Layer 3 is a ground layer. Layer 4 is a signaling layer.
As a surprise to myself, I managed to also get the layout of the DACQ done too. This could fit on a 2 layer board, as it has much less going on. The board is 4"x4". The layout of the DACQ can be seen below. Layer 1 is signaling with large power planes. Layer 2 has some signaling and large ground planes.
The test plans for when the boards come in are written. They consist mostly of sanity checks for the power, and then ensuring the communication protocols are working properly. An example of a test plan is shown below. All test plans can be found here.
BOM and Budget Update
The BOM for this phase is updated. It isn't at a state to place the order quite yet, but it is nearly there. This can be seen below.
The document can be seen here.
From this BOM, the budget remaining is calculated, as shown by the multiple figures below. Also shown is the contribution of each item makes to the total budget allocated for the CBOB and DACQ.