I got very hyped about the flexibility and carefully thought out design of the Gadgeteer system and the possibility of making my own DaisyLink modules. I did a reference design using a 14-pin 8-bit PIC chip which completely implements the DaisyLink protocol requiring just two external resistors and leaves 5 IO pins for the sensor/actuator interface with a wide range of digital and analog IO functions enabling just about any module type to be made with minimal extra components.
Then I costed it and got a shock! The BOM cost is completely dominated by the connectors! The specified connectors are VERY expensive - each costing about twice as much as the PIC chip and four being required per module (two male, two female). You can see this effect in the difference in cost between an EMX module and a FEZ Spider: electronically there are no additional active components, it is just the connectors and the circuit board (plus a couple of switches and LEDs). It adds $35 or 40% to the cost! If GHI decided to make a low-end Gadgeteer based on USBizi chips, the connectors would cost at least twice as much as the active components!
Specifying lower cost connectors would certainly help, but I cannot help thinking there must be a cleaver way of radically reducing the interconnect cost to make the system much more cost effective. Any thoughts anyone?
You forgot about the cable cost Digikey sells these cables for about $10 each and the socket is about $2 each! To buy cables/sockets from digikey, the FEZ Spider kit would have costed us double the price we sell it for!
GHI buys these connectors and cables in very high volumes so the cost is not a problem anymore. We had looked into this and studied it with the Gadgeteer team for more than 3 months before we decided on these cables/connectors.
Incorrect. Stay tuned for today’s (and future) announcements in this area.
I used retail pricing throughout in my comparisons. Use wholesale or bulk pricing consistently and the prices will be lower but the cost breakdown proportions will be the same (roughly).
Retail, you charge nearly $2 for the board connectors. The Spider and Hydra boards each have 14 connectors implying that the connectors account for $28 of the retail price of the board alone (not the kits). This is a lot for boards retailing in the $80 to $100 range. It also pretty much accounts for the $35 difference in price between EMX and Spider (leaving $7 for the extra circuit board and assembly).
Estimating $2 for a module PCB, adding $2 for the connector and $2.50 for the cable assembly, we get to a base retail BOM of $6.50 for a “simple” module and $8.50 for a DaisyLink module. Your button module at $5 seems to undermine this case, but I am guessing your module prices do not include the cable.
I think I can see a lower-cost (and in some other ways technically superior) scheme. Probably much too late, but I’ll post it anyway for academic interest when I have fully thought it through.
Digikey sells these cables for about $10 each and the socket is about $2 each! To buy cables/sockets from digikey, the FEZ Spider kit would have costed us double the price we sell it for!