USB-I/O Interface Adapter GPIO-24. Programmer's Reference Manual.
10.1. Frequency Counter Event
The GPIO_SET_FR_CNT_CFG command allows to switch on/off frequency counter mode on specified pin and to set the conditions of the event generation.
GPIO_SET_FR_CNT_CFG Command
| Byte 0 | GPIO_SET_FR_CNT_CFG | Command ID (0x16). | |
| Byte 1 | ECHO | Echo to associate a command with the response. | |
| Byte 2 | Bit 7..4 | ON | Frequency counter state. |
| Bit 3..0 | FR_CNT_NUMBER | ID number of the counter to measure frequency. | |
| Byte 3 | REPEAT | Repeat interval value in units of 100 ms. | |
| Byte 4 | COMP_VAL[2] | Threshold frequency (least significant byte). | |
| Byte 5 | COMP_VAL[1] | Threshold frequency (middle byte). | |
| Byte 6 | COMP_VAL[0] | Threshold frequency (most significant byte). | |
| Byte 7 | EVENT_COND | Condition of comparison. | |
Command is an 8-byte array of the following format:
- Byte 0: GPIO_SET_FR_CNT_CFG (0x16)
This byte contains command ID (command type). It should be set to 0x16.
- 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:
Bits 7..4 Bits 3..0 ON FR_CNT_NUMBER - Bits 7..4: ON
The frequency counter state (on/off):
1 – the pin will be switched to the frequency counter mode. GPIO_GET_CFG and GPIO_GET_PIN_CFG commands will return GPIO_CFG_FR_CNT (0x6) value for the pin. The pin can be used only by the frequency counter module;
0 – the frequency counter mode will be switched off on the pin. GPIO_GET_CFG and GPIO_GET_PIN_CFG commands will return GPIO_CFG_NOT_CONFIGURED (0xf) value for the pin. The pin can be used by any module.
- Bits 3..0: FR_CNT_NUMBER
The ID number of the frequency counter:
0 – frequency counter on A.3 pin;
1 – frequency counter on A.4 pin.
- Byte 3: REPEAT
This byte defines the repeat interval in units of 100 ms for the event GPIO_EV_FR_CNT generation. If this byte is non-zero, GPIO-24 adapter sends events each REPEAT*100 ms. For more detailed information see Section 10.1, “Frequency Counter Event”.
- Bytes 4..6: COMP_VAL
The threshold frequency to be compared with. The counter calculates frequency and constantly compares it with the threshold frequency specified in Bytes 4..6: COMP_VAL.
Byte 4: COMP_VAL[2] – least significant byte (low byte) of threshold frequency.
Byte 5: COMP_VAL[1] – middle byte of threshold frequency.
Byte 6: COMP_VAL[0] – most significant byte (high byte) of threshold frequency.
Frequency is specified in Hz in the range from 0 to 5,000,000 Hz (5 MHz).
- Byte 7: EVENT_COND
The condition of the comparison:
GPIO_FR_CNT_EV_NONE (0x00) – No events are sent by current frequency counter.
GPIO_FR_CNT_EV_BELOW (0x01) – Events are sent when the frequency is lower than the threshold value specified in Bytes 4..6: COMP_VAL.
GPIO_FR_CNT_EV_NOT_EQ (0x02) – Events are sent when the frequency is lower or higher than the threshold value specified in Bytes 4..6: COMP_VAL.
GPIO_FR_CNT_EV_EQ (0x03) – Events are sent when the frequency is equal to the threshold value specified in Bytes 4..6: COMP_VAL.
GPIO_FR_CNT_EV_ABOVE (0x04) – Events are sent when the frequency is higher than the threshold value specified in Bytes 4..6: COMP_VAL.
GPIO_FR_CNT_EV_ALWAYS (0x05) – Events are sent periodically with predefined interval specified in Byte 3: REPEAT.
For convenience GPIO_SET_FR_CNT_CFG_CMD structure is declared in reports.h file:
GPIO-24 adapter sends GPIO_SET_FR_CNT_CFG response after command execution.
GPIO_SET_FR_CNT_CFG Response
| Byte 0 | GPIO_SET_FR_CNT_CFG | Response ID (0x16). |
| Byte 1 | ECHO | Echo to associate a command with the response. |
| Byte 2 | ST | Status of the command execution. |
| Byte 3..7 | Reserved | Reserved |
Response is an 8-byte array of the following format:
- Byte 0: GPIO_SET_FR_CNT_CFG(0x16)
Response ID (response type). This byte will contain 0x16.
- Byte 1: ECHO
Echo byte copied from the corresponding command. It is used to associate the response with the specific command.
- Byte 2: ST
Status of the command execution:
GPIO_ST_SUCCESS (0x00) – Frequency counter was succesfully configured;
GPIO_ST_INVALID_FR_CNT_NUMBER (0x0A) – Invalid frequency counter ID has been specified (only 1 and 0 are valid);
GPIO_ST_UNKNOWN_EVENT_TYPE (0x0B) – Unsupported comparison condition has been specified.
- Bytes 3..7: Reserved
These bytes are reserved for future usage.
