USB-I/O Interface Adapter GPIO-24. Programmer's Reference Manual.

Command is an 8-byte array of the following format:

Byte 0: GPIO_SET_OUT_VAL (0x10)

This byte contains command ID (command type). It should be set to 0x10.

Byte 1: ECHO

This byte is used to associate a response received from GPIO-24 adapter with a specific command. Response will contain exactly the same value in its echo byte.

Bytes 2..7: Reserved

These bytes are reserved for future usage and must be set to 0.

Response is an 8-byte array of the following format:

Byte 0: GPIO_GET_CMP_CFG (0x0F)

This byte contains response ID (response type). This byte will contain 0x0F.

Byte 1: ECHO

This byte is used to associate a response received from GPIO-24 adapter with a specific command. Response will contain exactly the same value in its echo byte.

Byte 2: CMP_CFG

Bit 7	Bit 6	Bit 5	Bit 4	Bit 3..0
Reserved	CIS	CMP0_INV	CMP1_INV	MODE

Bit 7: Reserved

This bit is reserved for future usage.

Bit 6: CIS

Comparator Input Switch bit. The comparator input switch bit is used only in Four Inputs Multiplexed to Two Comparators mode (MODE = 6).

If CIS = 0:

• C.1 pin is connected to CMP0 V_IN-;

• C.2 pin is connected to CMP1 V_IN-.

If CIS = 1:

• C.6 pin is connected to CMP0 V_IN-;

• C.5 pin is connected to CMP1 V_IN-.

Bit 5: CMP0_INV

CMP0 comparator output inversion bit.

If CMP0_INV = 1, CMP0 comparator output is inverted:

• 1, if V_IN+ < V_IN-;

• 0, if V_IN+ > V_IN-.

If CMP0_INV = 0, CMP0 comparator output is not inverted:

• 1, if V_IN+ > V_IN-;

• 0, if V_IN+ < V_IN-.

When C.4 I/O pin is used to output comparator results, its output is also inverted (MODE = 1, 3 or 5).

Bit 4: CMP1_INV

CMP1 comparator output inversion bit.

If CMP1_INV = 1, CMP1 comparator output is inverted:

• 1, if V_IN+ < V_IN-;

• 0, if V_IN+ > V_IN-.

If CMP1_INV = 0, CMP1 comparator output is not inverted:

• 1, if V_IN+ > V_IN-;

• 0, if V_IN+ < V_IN-.

When B.3 I/O pin is used to output comparator results, its output is also inverted (MODE = 3 or 5).

Bits 3-0: MODE

The operation mode USB-I/O adapter comparator module. There are eight operation modes, they are described in Section 8.1, “Modes of operation for comparator module”.

Byte 3: VREF

This byte is used to retrieve comparator voltage reference module configuration. For more detailed information see Section 8.2, “Comparator voltage reference module”.

The comparator voltage reference module is only available in Four Inputs Multiplexed to Two Comparators mode (MODE = 6). In other modes this byte is reserved and must be ignored.

Voltage reference module configuration (VREF) is a bit field of the following format:

Bit 7	Bit 6	Bit 5	Bit 4	Bit 3..0
Reserved	OUTPUT	EXT_SOURCE	RANGE	MULTIPLIER

Bit 7: Reserved

This bit is reserved for future usage.

Bit 6: OUTPUT

Voltage reference module may also output the voltage reference (CV_REF) onto C.5 I/O pin:

• If OUTPUT = 1, CV_REF is output on C.5 I/O pin;

• If OUTPUT = 0, CV_REF is disconnected from C.5 I/O pin.

You can use the C.5 pin to check the reference voltage with oscilloscope. Due to the limited current drive capability, a buffer must be used on the voltage reference output for external connections to CV_REF.

Bit 5: EXT_SOURCE

The comparator reference voltage module’s power supply may be provided either from the GPIO-24 adapter V_DD/V_SS or from an external source.

• If EXT_SOURCE = 1, the voltage reference module uses C.5 (V_REF+) and C.6 (V_REF-) pins as voltage source:

  CVR_SRC = V_REF+- V_REF-

• If EXT_SOURCE = 0, the voltage reference module uses USB-I/O adapter positive (V_DD) and negative (V_SS) supply as voltage source:

  CVR_SRC = V_DD – V_SS

Bit 4: RANGE

The comparator voltage reference module provides two ranges of output voltage (CV_REF), each with 16 distinct levels. Use Bit 4: RANGE to determine which range has been selected. The primary difference between the ranges is the size of the steps selected with Bits 3-0: MULTIPLIER. That is why one range offers finer resolution but shorter interval of possible values (RANGE = 0).

Bits 3-0: MULTIPLIER

With Bits 3-0: MULTIPLIER you can determine the output voltage (CV_REF) of voltage reference module.

Use the following equations to calculate the CV_REF:

If RANGE = 1:

CV_REF = (CVR_SRC /24) x MULTIPLIER;

MULTIPLIER = 24* (CV_REF/ CVR_SRC).

If RANGE = 0:

CV_REF = (CVR_SRC /4) + ((CVR_SRC /32) x MULTIPLIER);

MULTIPLIER = 32*( CV_REF / CVR_SRC) – 8.

Use Bit 5: EXT_SOURCE to determine CVR_SRC.

Byte 4: REPEAT0_LSB

Byte 4: REPEAT0_LSB contains 8 least significant bits of repeat interval value for CMP0 comparator. For more detailed information see Section 8.3, “Comparator module event”.

Byte 5: REPEAT0_MSB / COND0

Bits 7..4	Bits 3..0
REPEAT0_MSB	COND0

Bits 7..4 REPEAT0_MSB

Bits 7..4 REPEAT0_MSB are 4 most significant bits of repeat interval value for CMP0 comparator. For more detailed information see Section 8.3, “Comparator module event”.

Bits 3..0 COND0

The low nibble of Byte 5 defines when USB-I/O adapter sends events (GPIO_EV_CMP) for CMP0 comparator:

GPIO_CMP_EV_NONE (0x00)

The comparator does not send events.

GPIO_CMP_EV_CHANGE (0x01)

The event is sent when the comparison result changes.

GPIO_CMP_EV_ALWAYS (0x02)

The event is sent periodically with the predefined repeat interval. This interval value is specified in Byte 4: REPEAT0_LSB (8 least significant bits) and Bits 7..4 REPEAT0_MSB in Byte 5 (4 most significant bits).

Byte 6: REPEAT1_LSB

The bits of Byte 6: REPEAT1_LSB are 8 least significant bits of repeat interval value for CMP1 comparator. For more detailed information see Section 8.3, “Comparator module event”.

Byte 7: REPEAT1_MSB / COND1

Bits 7..4	Bits 3..0
REPEAT1_MSB	COND1

Bits 7..4 REPEAT1_MSB

Bits 7..4 REPEAT1_MSB are 4 most significant bits of repeat interval value for CMP1 comparator. For more detailed information see Section 8.3, “Comparator module event”.

Bits 3..0 COND1

The low nibble of byte 7 defines when USB-I/O adapter sends events (GPIO_EV_CMP) for CMP1 comparator:

GPIO_CMP_EV_NONE (0x00)

The comparator does not send events.

GPIO_CMP_EV_CHANGE (0x01)

The event is sent when the comparison result changes.

GPIO_CMP_EV_ALWAYS (0x02)

The event is sent periodically with the predefined repeat interval. This interval value is specified in Byte 6: REPEAT1_LSB (8 least significant bits) and Bits 7..4 REPEAT1_MSB in Byte 7 (4 most significant bits).