PSAS/ CanNodes

LV2 CAN Nodes

LV2 consists of a main processor - the "Flight Computer" which is a 586 PC-104 board - and a dozen tiny little boards strung out on the CAN bus. These dozens of little boards are each run by a small microcontroller (currently the PIC18F458) and perform all of the sensing and actuation for the vehicle.

Since each of the boards has the same microcontroller, we've decided to break the nodes up into virtual "sections". Each section is a schematic and layout all to itself; using a common interconnect pattern, these layouts are then laid next to each other by a Gerber editor application. It's a clever way to eek some professional quality features from a shareware program (EAGLE).

CAN Node "Sections":

CanNodeSectionProcessor The section with the PIC18F458, 12 to 5V switching power supply, oscillator, an optional Vref and ICD plug-in.
?CanNodeSectionInterface The section with the CAN and power connectors, all still TBD.
?CanNodeSectionMechanical The section with the space for fasteners and possibly a card cage - all TBD.

LV2-frontend.png LV2-frontend.pdf

Can Node "Application" Sections:

CanNodeSectionAppPyro The application section with the pyrotechnic igniter firing circuits, amateur 2m radio receiver with DTMF decoder, and Li backup power supply.
CanNodeSectionAppPower The application section with a Smart Battery System (SBS) Level 2 charger, various power devices, and Umbilical cord connector.


ICD2 to CAN Node cabling information

Used PIC18F458 Pins

The "next generation" PIC nodes are converging to a single design, with a neat little CAN connector, switched power supply (SPS) and for critical nodes, a highly-available power supply (HAP). Also, all nodes must have an oscillator, ICD2 pins, MCLR, etc.

Name Pin Type Modules Description
MCLR 18 in ALL Master reset
OSC1 30 in ALL 10MHz crystal input
OSC2 31 out ALL 10MHz crystal output
RA0 19 in (A) HAP "HAPBCurr" - HAP battery current measurement
RA1 20 in (A) HAP "HAPBVolt" - HAP battery voltage measurement
RA2 21 in (A) HAP "HAPBTemp" - HAP battery temperature
RA4 23 OC out SPS "SPSOFF\" - Shuts down SPS.
RB2 10 out ALL CAN TX
RB3 11 in ALL CAN RX
RB4 14 out ALL CAN transciever (MCP2551) slope/reset
RB5 15 i/o ALL LED/switch combo ("omnibutton", Error LED, etc)
RB6 16 out ALL ICD2 (PGC) - SET TO OUTPUT so it doesn't fload wo/ICD2
RB7 17 out ALL ICD2 (PGD) - SET TO OUTPUT so it doesn't fload wo/ICD2
RE0 25 out HAP "HAPTrickle" - Enables trickle charging of HAP battery
RE1 26 our HAP "HAPFast" - Enables fast charging of HAP battery (Overrides trickle charging)
RE2 27 out HAP "HAP_Off" - Power down HAP

in = digital input, out = digital output, oc = open collector, in (A) = analog input, HAP = Highly Available Power supply, SPS = Switching Power Supply.

There are some pins which usually get used for the same thing: RB0/1 are good for edge-triggered interrupts, RC6/7 are the onboard UART pins, etc.