Time for another test of capability. These tests help us check the hardware compiler performance to a actual built commercial board. Some of the items for us to check are:
- How closer are we able to design the board with respect to requirements?
- Is there any possibility of optimization among circuit tree outputs?
- What is the board cost compared to the comparison board?
- Circuit Tree designs would be different than the designed board. How do we verify the design?
This time we compare the capability of circuit tree with another commercial board in the market available from olimex. It is a great open source hardware board available at a competitive price with great support from olimex.
Let us again pick the requirement of the board from site :
- STM32F407ZGT6 microcontroller
- JTAG connector with ARM 2×10 pin layout for programming/debugging
- Ethernet 100Mbit
- UEXT connector (UEXT is a board to board connector which supports three serial communication interfaces – I2C, SPI and RS232. There is also 3.3V line and GND.)
- USB host
- USB OTG
- Input DC DC power supply which allows operation from 6-16VDC source
- Power and user LEDs
- Reset and user buttons
- 4 full 20-pin Ports with the external memory bus for add-on modules
- Arduino platform with unsoldered headers
- 4 rubber pads for the mount holes
- PCB: FR-4, 1.5 mm (0.062″), soldermask, silkscreen component print
- Dimensions: 101.6 x 86mm (4 x 3.4″)
- Boards costs 40USD in quantity of unit 1 as per olimex.
Requirement entry in Circuit Tree
Let us add this requirement on circuit tree requirement editor:
We add requirements in the tool by adding spi, i2c and other buses to a UEXT connector. Similarily for the Arduino connector the spi and uart bus signals are routed to the connectors. We additionally add the GPIO connector having close to 11 pins. Additional interfaces such as ethernet with lan8710, usb type AB port with esd protection, sd card and jtag ports are added as per the snapshots below.
Circuit Tree hardware compiler next finds the controller which can support these function. Circuit Tree returns close to 186 parts. We have option to select STM32F407ZGT6 or STM32F407ZET6 with several other parts. We choose STM32F407ZET6 as olimex schematic has this part designed into it.
We next select power of 6V to 14V as required in the requirement and get the schematic design generated in a minutes time. You would notice that the BOM cost derived from Octopart comes to USD 51. The pdf, bom and eagle schematic design is available at link
We select a board size of 130mm x64 mm.
Output placement file is shown below with the constraint that all components be placed on the top side of the board. The red color denotes the placement of the component on the top side of the board. We need to work more on the board by adding the constraints to the board footprints. The arduino connectors are misplaced in the picture below. Files are uploaded at link
Comparison between two designs:
- SDHC section visual check: Circuit tree auto creates processor symbol based on the bus sections and adds them to the connector page. All pins of the connector and the processor pins are the same for sections stated below:
micro sd interface check
- JTAG section visual check:
Jtag connection visual check
- USB section visual check: Two usb otg ports are compared. The connector pinouts, vbus generators and esd connections can be checked in the schematic.
- Ethernet RMII section: Comparison of lan8710 and STM32F407ZET6 connections are done. All controllers pins are the same except for the PG11 which in case of circuit tree schematic is PB11 which is correct as per pin mux.
lan8710 ethernet schematic
- UEXT connector connections: The connections of the controller pins and the UEXT assignment is different than allocated. The connector pin definition is also different than the one desired.
- Other differences:
- Power, clock and reset generation is different in circuit tree. It shows that circuit tree can generates it own power supply connections based on what it calculates the extremes.
- Some of BOM parts selected by circuit tree are high is cost. One of the examples being integrated magnetics which cost close to usd 10. We would address this concern once we have sufficient parts in the library which would provide value range to the user.
- Arduino connectors are not compared as the pin assignment and gpio connections are not as per connector requirements even though the muxing from controller is correct. In the next release we would have new feature to change the connector pin outs.
- IFC pin connections failed as circuit tree does not generate a connection where it observes conflict of IO’s. The commercial schematic uses jumpers to isolate segments which we can also support at a later date.
- The placement of the design was not the same as the olimex board. We are in process of improving the constraint addition which would help to create more custom designs.
It was a long post with visual comparison of the two boards. Write back to us at email@example.com with your feature requests and suggestions.