USB-I/O Interface Adapter GPIO-24. Programmer's Reference Manual.
10.3. GPIO_GET_FR_CNT_CFG (0x17)
The GPIO_GET_FR_CNT_VAL command retrieves current frequency measured by specified frequency counter.
GPIO_GET_FR_CNT_VAL Command
| Byte 0 | GPIO_GET_FR_CNT_VAL | Command ID (0x18). |
| Byte 1 | ECHO | Echo to associate a command with the response. |
| Byte 2 | FR_CNT_NUMBER | ID number of the frequency counter to retrieve frequency from. |
| Byte 3..7 | Reserved | Reserved (must be 0). |
Command is an 8-byte array of the following format:
- Byte 0: GPIO_GET_FR_CNT_VAL (0x18)
This byte contains command ID (command type). It should be set to 0x18.
- 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: FR_CNT_NUMBER
The ID number of the frequency counter to retrieve frequency from:
0 – frequency counter on A.3 pin;
1 – frequency counter on A.4 pin.
- Bytes 3..7: Reserved
These bytes are reserved for future usage and must be set to 0.
For convenience GPIO_GET_FR_CNT_VAL_CMD structure is declared in reports.h file.
GPIO-24 adapter sends GPIO_GET_FR_CNT_VAL response after command execution. The current frequency is specified inside the response.
GPIO_GET_FR_CNT_VAL Response
| Byte 0 | GPIO_GET_FR_CNT_VAL | Response ID (0x18). |
| Byte 1 | ECHO | Echo to associate a command with the response. |
| Byte 2 | ST | Status of the command execution. |
| Byte 3 | FR_CNT_NUMBER | ID number of the frequency counter, from which frequency has been retrieved. |
| Byte 4 | FREQUENCY[2] | Frequency in Hz (least significant byte). |
| Byte 5 | FREQUENCY[1] | Frequency in Hz (middle byte). |
| Byte 6 | FREQUENCY[0] | Frequency in Hz (most significant byte). |
| Byte 7 | Reserved | Reserved |
Response is an 8-byte array of the following format:
- Byte 0: GPIO_GET_FR_CNT_VAL (0x18)
Response ID (response type). This byte will contain 0x18.
- 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 has been succesfully retrieved;
GPIO_ST_INVALID_FR_CNT_NUMBER (0x0A) – Invalid ID number of the frequency counter has been specified (only 0 and 1 are valid).
- Byte 3: FR_CNT_NUMBER
The ID number of the frequency counter, from which current frequency has been retrieved:
0 – frequency counter on A.3 pin;
1 – frequency counter on A.4 pin.
- Byte 4..6: FREQUENCY
The current frequency in Hz.
Byte 4: FREQUENCY[2] – least significant byte (low byte) of frequency.
Byte 5: FREQUENCY[1] – middle byte of frequency.
Byte 6: FREQUENCY[0] – most significant byte (high byte) of frequency.
- Byte 7: Reserved
This byte is reserved for future usage.
For convenience GPIO_GET_FR_CNT_VAL_RSP structure is declared in reports.h file.
