System for ink short protection

An ink short protection system for signaling to inkjet printheads comprising:

• a differential signaling driver having a first and a second terminal;
• a differential signaling receiver having a first and a second terminal;
• a first capacitor in series between the first terminals;
• a second capacitor in series between the second terminals;
• parallel means for reducing charge accumulation on the capacitors;
• and
• active means for manipulating a data stream transmitted from the driver by steering current to the first driver terminal for a logic 1 data element and steering current to the second driver terminal for a logic 0 data element, whereby signals present on the first and second driver terminals tend to cancel the charge applied to the blocking capacitors by previous signals.

A method of ink short protection for differential signaling to inkjet printheads comprising:

• blocking a first DC current between a first terminal of a differential signaling driver and a first terminal of a differential signaling receiver;
• blocking a second DC current between a second terminal of the driver and a second terminal of the receiver;
• and
• manipulating a data stream which is transmitted from the driver to the receiver whereby signals present on to first and second terminals of the driver tend to cancel the charge applied to the blocking capacitors by previous signals, wherein manipulating the data stream comprises:
• segmenting the data stream into data packets;
• determining whether a majority of logic 1 data elements or a majority of logic 0 data elements have been transmitted by the driver;
• examining each data packet prior to transmission by the driver to determine whether a majority of logic 1 data elements or a majority of logic 0 data elements are in the data packet;
• inverting the data elements of the data packet prior to transmission by the driver if necessary to keep the number of transmitted logic 1 data elements approximately equal to the number of logic 0 data elements;
• and
• combining a data header with the data packets, including an invert data element to indicate whether the data elements of the data packet being transmitted by the driver are inverted.

An ink short protection system for connections to inkjet printheads comprising:

• an LVDS driver having a first and a second terminal;
• an LVDS receiver having a first and a second terminal;
• a first capacitor in series between the first terminals;
• a second capacitor in series between the second terminals;
• passive circuitry for dissipating charge accumulated on the capacitors including:
• a first bleeder resistor connected in parallel across the first capacitor;
• and
• a second bleeder resistor connected in parallel across the second capacitor;
• and
• active circuitry for manipulating a data stream transmitted from the driver by steering current to the driver first terminal for a logic 1 data element and alternatively steering current to the driver second terminal for a logic 0 data element, whereby signals present on the first and second driver terminals tend to cancel the charge applied to the capacitors by previous signals, and wherein the active circuitry includes a configuration to:
• segment the data stream into data packets;
• track whether a majority of logic 1 data elements or a majority of logic 0 data elements have been transmitted by the driver;
• examine each data packet prior to transmission by the driver to determine whether a majority of logic 1 data elements or a majority of logic 0 data elements are in the data packet;
• invert the data elements of the data packet prior to transmission by the driver if necessary to keep the number of transmitted logic 1 data elements approximately equal to the number of logic 0 data elements;
• and
• combine a data header with the data packets, including an invert data element to indicate whether the data elements of the data packet being transmitted by the driver are inverted.

An ink printhead comprising:

• a plurality of ink drop generators;
• a differential signal receiver;
• and
• circuitry including a configuration to interpret binary packets received by the differential receiver, wherein:
• the binary packets include an invert bit and data bits;
• and
• the circuitry reads the invert bit from each binary packet and inverts the data bits when indicated by the invert bit prior to using the data bits to trigger the ink drop generators.

An ink short protection system for signaling to inkjet printheads comprising:

• a differential signaling driver having a first and a second terminal;
• a differential signaling receiver having a first and a second terminal;
• a first capacitor in series between the first terminals;
• a second capacitor in series between the second terminals;
• means for reducing charge accumulation on the capacitors;
• and
• means for:
• determining whether a majority of logic 1 data elements or a majority of logic 0 data elements have been transmitted by the driver;
• examining each data packet prior to transmission by the driver to determine whether a majority of logic 1 data elements or a majority of logic 0 data elements are in the data packet;
• inverting the data elements of the data packet prior to transmission by the driver if necessary to keep the number of transmitted logic 1 data elements approximately equal to the number of logic 0 data elements;
• and
• combining a data header with the data packets, including an invert data element to indicate whether the data elements of the data packet being transmitted by the driver are inverted.