Picobus connector wiring

The bus is based on a small IDC10 connector, compatible with DIN41651 and MIL-C-83503, without retaining clips. Material is Glass filled polyester, UL94V-0 rated. The cable is 105 degrees rated, UL recognised (generally UL VW-1 flame retardant). All contacts are gold plated.

	Name	Function
Pin 1	Q0	Mux select	Switch to Vcc at time T=0
Pin 2	DEV	Data bit, even	Microprocessor port bit
Pin 3	Q1	Mux select	Switch to Vcc at time T=1
Pin 4	DOD	Data bit, Odd	Microprocessor port bit
Pin 5	Q2	Mux select	Switch to Vcc at time T=2
Pin 6	Q3	Mux select	Switch to Vcc at time T=3
Pin 7	SCL	i2c bus	Open drain, pullup to Vcc
Pin 8	Vcc	Power supply	Usually +5v, cable rating 1A
Pin 9	SDA	i2c bus	Open drain, pullup to Vcc
Pin 10	Gnd	System Ground	-

Picobus pin layout - component side view

Picobus wire diagram

Mux selects	Q0,Q1,Q2,Q3	Active high select signals
Data bits	DEV, DOD	Microprocessor I/O port signals
i2c	SDA, SCL	Philips i2c
Power	Vcc, Gnd	Vcc usually +5v

The active high multiplex selects, Q0-Q3, are switches to Vcc that are continuously scanned by the host microprocessor. Generally, each Mux select is activated for a period of 0.5ms-1ms in sequence, with each Mux select having an ON duty cycle of 10-25%.

When used in conjunction with the multiplex selects, the two microprocessor port signals DEV,DOD send or receive multiplexed data. For instance, if multiplexing LED indicators, the two Data bits and four Mux selects allow a total of 8 indicators to be attached to one Picobus connector.

The DEV and DOD lines may (alternatively) be used as normal unmultiplexed I/O port signals.

The AirION implements several Picobus connectors. Each has two dedicated microprocessor port bits: DEV,DOD, - while the remaining Picobus signals are common to all connectors.

Picobus Connector	DEV signal	DOD signal
PicoA	P0.0	P0.1
PicoB	P0.2	P0.3
PicoC	P0.4	P0.5

Simple LEDs and switches may require no power, and attach between one of the Q0-Q3 lines, and DEV or DOD. More complicated circuits will require power from Gnd and Vcc, and will attach through the i2c bus, and or possibly the port signals. Some circuitry may treat the Q0-Q3 signals as TTL levels, to enable drivers or latches connected to DEV and DOD. The i2c bus is also available to facilitate expansion using that family of devices.

This page had a Maintenance update: 23 April 2013

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