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PET Node components and BOM
The PET node seems to consist of three main parts:
- Ethernet PoE interface, including the Ethernet PHY transformer
- MCU functionality, including the Ethernet PHY
- An optional ID chip
- I/O functionality for automation and instrumentation
Most probably we want to have direct fixed connector to the PCB. One option is to use the standard "110" punchdown tools. There are at least two connectors for direct 110 punchdown to PCB connectivity:
- Belfuse SS-51
- PT-5002
- 110e8-pcb not available at the moment
- 110e4-pcb
- Kinsun 5803-8 (L 32.8 x W 5.3 x H 11.8)
- Kinsun 5802-8 (L 32.6 x W ? x H 10.6?mm)
- Anshi XL-029A (L 32.7 mm x W 8mm x H 14mm)
- Anshi XL-029C (L 30 mm x W 6.25mm x H 14.6mm)
- Anshi XL-029D (L 30.5 mm x W 6.25 mm x H 16 mm)
- Anshi XL-029E (L 30.5 mm x W 6.25 mm x H 14.6 mm)
- Siemon Pressfit (L 30.5 x W 6.1 x H 16)
- AMP 558815-1 ()
The most accurate keyword is perhaps "idc-110 pcb connector".
These all seem to cost less than $1.00 a piece in small numbers, down to $0.02 in large numbers.
If we want to support 802.3af compliant PoE, we basically need to have a controller for it. Linear LTC4265 is a ready-made controller that includes a switching regulator. However, it is a little bit pricey...
LTC4265 has a separate 802.3af controller and a separate flyback switching regulator driver. The latter can be driven on as low primary voltage as 9V; hence, with proper design it should be possible to use a single PCB with LTC4265, providing options both for 802.3af Mode B compliant -48VDC and for home brewn -24VDC (or even lower). (Whether the switching regulator driver really requires negative voltage needs to be checked...)
Other PoE PD controllers include TI TPS237x (see the reference design PMP717), e.g. TPS23753A, Maxim MAX5982A, OnSemiconductor NCP1080, National/TI LM5070 (expensive?), ST PM8800 and PM8803, Si Si3402. Most (all?) of of these require an external flyback FET, which may be relatively expensive.
An alternative might be a lower-power switching regulator with some external analog components, but that may turn out to be even more expensive.
The power MOSFET price seems to depend on on-state resistance Rds, Drain-Source voltage Vds, and continuous Drain current Id. At Farnell FI, selecting Rds < 0.8 Ohm, one can find a number of Vds >= 60V, Vid = 300..500 mA, at around ~€0.05 a piece. At Rds < 0.1 Ohm, the price goes up to ~€0.20-0.40.
A probably relatively expensive component. Need to look for an inexpensive, lower-power one. LTC4263 data sheet examples use Pulse PA1133, but even Pulse PA1130 seems to be too "heavy" (3W) for our use.
Coilcraft has lots of different flybacks, also specifically for (http://www.coilcraft.com/poe_ep.cfm)[PoE PD], but their pricing is very high on low volumes. If we'd be able to order 5000 or more, the price would go down to sub-dollar range; in small volumes the price appears to be well over two dollars.
Pulse HX1188
The MCU functionality has two main options:
- A low end Cortex-M0 MCU connected with SPI to a separate Ethernet chip, the latter including the PHY.
- A higher end Cortex-M3/4 MCU with Ethernet MAC, with RMII interface to an Ethernet PHY chip
Olimex STM32-P407 uses Mikrel KS8721BL, but it seems to be more expensive than Mikrel KSZ8021/31RNL.
ST's STM32F107 demonstration board compatible ST802RT1 board. [ST802RT1A Ethernet PHY demonstration board with STM32F107 controller add-on board] (http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATA_BRIEF/CD00266773.pdf).
These must include the PHY; if you find one that doesn't, remove it, as a separate PHY adds one chip and unnecessary cost. In low volumes the chip count will dominate the price.
The low-end ones include only the Ethernet MAC. Some of the higher-end ones also TCP/IP. We are focusing on the low-end ones, as even a lowly Cortex-M0 is quite capable of implementing the needed basic UDP/IP functionality.
Microchip ENC28J60 or ENC424J600. Asix AX88796C. Micrel KSZ8851SNL. Wiznet W5100.
ST STM32F05x series are available both in small packages (LQPF32 and ULQPF32) and the relatively large LQFP64. The latter is pin compatible with the STM32F107, STMF2x7 and even STMF4x7 in LQFP64.
NXP LPC111x is available in tiny packages, down to 20 pins.
The low-end ARM Cortex MCUs do not have built-in Ethernet yet. The cheapest ones appear to be in the Cortex-M3 and Cortex-M4 series.
From ST, the cheapest Ethernet MCU seems to be STM32F107RBT6. In LQF64 it is quite but not fully pin-compatible with the low-end STM32F05x, as well as the even higher end STM32F217 and the even higher end STM32F407 and STM32F417.
From NXP there is at least [LPC1767FBD100], LPC1764FBD100 and mainly LPC1758FBD80 in LQFP80. From Atmel, SAM3X in LQFP100 (or bigger). However, these have big packages (minimum 64 leads as LQFP64, typically 80 or 100 as a BGA) and lots of features we don't need.
STM32F051, STM32F107, STM32F217, STM32F407 and STM32F417 in LQFP64 are quite pin-compatible, with only a few pins having differing functions. Hence, it should be possible to create a PCB that could have either one of the bigger chips, which include Ethernet functionality, or the lowest end STM32F051 and e.g. ENC28J60. However, both the Cortex-M0 and the Cortex-M4 chips in LQFP64 seem to be of short supply, at least at the moment. The Cortex-M0 chips are available mainly in the ULQFP32 package, while the Cortex-M4 chips mainly in the bigger packages. However, with some clever solutions should be possible to fit STM32F051 in both LQFP64 and (U)LQFP32 in the same location on a PCB, with the (U)LQFP32 inside the LQFP64. For the bigger packages it may be necessary to do another PCB layout.
NXP doesn't seem to offer such pin compatibility.
We haven't studied pin compatibility from the other vendors, as they don't provide low-end Cortex-M0 processors at the time.
Atmel ATSHA204
At least STM32F100 has internal unique ID.
Early cost estimation
| Component | Example | á@1 | á@100 | Source |
|---|---|---|---|---|
| PoE PD controller | Linear LTC4267CGN | $2.75 | $2.36 | Linear US 2012-10-08 |
| PoE PD controller | TI TPS23753APW | $3.40 | $1.64 | [Digikey](http://www.digikey.com/product-detail/en/TPS23753APW/296-24928-5-ND/2122269) 2013-01-01, Also Mouser |
| Eth PHY transformer | PULSE HX1188NL | $2.40 | $0.93 | Verical 2012-10-08 |
| Flyback transformer | Coilcraft D1766-ALB | $2.70 | ? | Coilcraft 2012-10-06 |
| Flyback FET | €0.40 | €0.20 | Farnell FI 2012-10-14 | |
| Ethernet Jack with magnetics | Bel Fuse 0813-1X1T-57-F | E5,01 | E3,01 | http://www.digikey.fi/product-detail/en/0813-1X1T-57-F/507-1421-ND/2107986 |
Several MCU alternatives
| Component | Example | á@1 | á@100 | @1000 | Source |
|---|---|---|---|---|---|
| Ethernet controller | Microchip ENC28J60-C/SS | €2.44 | €2.07 | Farnell FI 2012-10-08 | |
| Cortex-M0 | ST STM32F050K4U6A | €1,64 | €1,29 | Farnell FI 2012-10-08 | |
| Cortex-M0 | ST STM32F051R4T6 | €2,88 | €2.50 | 1.82 | Mauser FI 2012-10-10 |
| Cortex-M3 (low end) | ST STM32F100C4T7B | €1,94 | €1,46 | Farnell FI 2012-10-08 |
A separate Ethernet-PHY. Several MCU alternatives.
| Component | Example | á@1 | á@100 | Source |
|---|---|---|---|---|
| Ethernet PHY | Mikrel KSZ8031RNL TR | €1.42 | €0,82 | Farnell FI 2012-10-08 |
| Cortex-M3 w/Eth | ST STM32F107RCT6 | €5,78 | Farnell FI 2012-10-08 | |
| Cortex-M4 w/Eth | ST STM32F407RCT6 | €~12? |
| Component | Example | á@1 | á@100 | Source |
|---|---|---|---|---|
| ID chip | ATMEL ATSHA204-TSU-T | €0.53 | €0,44 | Mauser FI 2012-10-12 |