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bbb hardware spec
###CAN bus
| CAN Bus | Port | isolation |
|---|---|---|
| VE.Can | CAN1 | YES |
| CAN-BUS | CAN0 (3rd party devices: e.g. LG Chem battery) | NO |
| (Bus driver: SN65HVD1050 (recommend a 3.3V driver instead) (MPPT, CCGX...)) |
VE.Can bus must/will be isolated, including the power supply for the transceiver. An alternative to the ADµM isolators must be found because they are $5,32 each Using the ISO1050 with a separate dc/dc will probably be most economic. BBB will not power any other nodes, other than its own transceiver
###UARTS
| Function | Port | Isolation | tty |
|---|---|---|---|
| Debugging Console | UART0 | NO | /dev/ttyO0 |
| VE.Direct1 | UART2 | YES | /dev/ttyO2 |
| VE.Direct2 | UART4 | YES | /dev/ttyO4 |
| VE.Bus | UART5 (with MK3 µC) | YES | /dev/ttyO5 |
| UART3 (=TX only) | conflicts with SPI_1 CS1 | (NOT USED) |
- Galvanic isolation between BBB and MK3. No isolation between MK3 and VE.Bus, only an RS485 transceiver
- VE.Bus Panel detect connected to VE.Bus GND
- VE.Bus standby/wake_up driven by BBB through optocoupler
- MK3 PIC microcontroller powered from BBB cape
- MK3 RST driven by BBB
- MK3 BRK driven by BBB (Provisional, expected not to be needed in future)
###RTC PCF8523T on I2C2.
... on I2C2. Currently not populated. Could be used to identify cape type and version.
There’s only 1 USB port on the BBB. Use an external 3rd party USB hub. Users that need only 1 port don’t need the HUB. Hub can be powered from the Cape.
5 pulse counting GPIO inputs.
- Pump counter For e.g. solar water pumps in Africa
- S0 counter: for kWh, Heating, gas and water metering.
- S0 is standardized acc. EN 62053-31
- Minimum pulse/pause length is 30ms, so the maximum pulse frequency at 50% duty is about 17Hz
- 3 tank level sensors, e.g. fresh water, black water, fuel.
- connects to standard tank senders, 0...300
1 input, 0...70V
Dropped because it won't be accurate since not differential, and no sense wires. Customers can better install a BMV or use battery voltage measured by connected solar charger or something else.
- 2 inputs
- LM335Z sensors (the exact same sensors that the Multi's use)
8-70V power input. Output 5V 2500mA. The BBB needs 1A for the board only + 500mA for the USB port. To power an external HUB + USB devices an extra 500mA...1A is required.
The BBB needs a 4.3...5.8V supply on the barrel connector, or the header. (=VDD_5V on the expansion headers). Rise time from 100mV to 4.3V needs to be <50ms. The power input is 20V tolerant, but the BBB's SOC is not powered outside the VDD range.
- 1 user programmable relay.
- Space for a second relay.
- Must maintain position during reboot (For example when updating), but must drop when power fails (to avoid unwanted generator starts when power returns)
An LCD will not be inluded: the system will only run headless.
Depending on cost and space, a buzzer may be included.
The board would ideally be the same size as the BBB.
The BBB control will be housed in a plastic box with sufficient room for cabling. Housing style will be like our current plastic housings, but with a junction-box base. See picture below. Sizes will match requirements off course. Connections will be made on the bottom side only through cable gland holes. This will provide at least IP64.
###Buttons on cape Not needed, except for reset which doesn’t take up a GPIO.
Seeedsudio's BeagleBone Green has no HDMI, and is therefore about $10 cheaper The BB Green has 2 Grove connectors: one is on UART2, so takes out a VE.Direct port if wanted. The other Grove connector uses I2C2, so it can be used instead of the secondary CAN bus.
- PWM output: e.g. to allow power control of a water heater to exactly match supply and demand
- Bluetooth
- housing