The Cron driver provides scheduled task execution for the Weble universal gateway. It uses the standard cron expression format to define time-based schedules. At each scheduled time, the cron address emits a configurable value that can trigger routes — enabling time-based automation without any external system.
The Cron driver is essential for:
- Periodic data collection — trigger a read on a Modbus or BACnet address at fixed intervals or specific times.
- Scheduled reports — generate and send CSV exports every day at midnight.
- Time-based alerts — send a daily status email or SMS at a specific time.
- HVAC schedules — switch setpoints between day/night modes based on time of day and day of week.
- Watchdog timers — periodically write a keepalive value to a register.
The key concept is simple: the address name is the cron expression, and at each scheduled tick, the address emits its configured value. This value can then be routed to any destination address on any protocol.
¶ 1. Getting started
¶ 1.1 Gateway configuration
Create a new gateway and select the Cron driver. The configuration is minimal — only a Name and optional Description.
¶ 1.2 Creating a scheduled task
Insert a new address. The address name is the cron expression that defines the schedule. The Cron value field defines what value is emitted at each tick (default: 1).
For example, to emit the value 1 every minute:
- Address name:
* * * * * - Value:
1
To emit the value 42 every day at 8:00 AM:
- Address name:
0 8 * * * - Value:
42
¶ 1.3 Using with routes
The real power of the Cron driver comes from combining it with routes. Create a route with the cron address as the source and any other address as the destination.
Example: Read a Modbus sensor every 15 minutes
- Create a cron address:
0,15,30,45 * * * *with value1. - Create a route:
0,15,30,45 * * * *→%M1(Modbus register). - Set the route type to read — the cron tick triggers a read on the Modbus register.
Example: Send a daily status email
- Create a cron address:
0 8 * * 1-5(weekdays at 8 AM) with value"Daily status report". - Create a route:
0 8 * * 1-5→admin@company.com(SMTP address). - The email is sent every weekday morning with the configured text.
Example: Switch HVAC mode between day and night
- Create a cron address:
0 7 * * 1-5with value21(day setpoint). - Create another cron address:
0 19 * * 1-5with value18(night setpoint). - Route both to the BACnet setpoint: →
%bac:local/analogValue:1.
¶ 2. Gateway parameters
| Label | JSON Key | Description |
|---|---|---|
| Name | name | A descriptive name for this Cron gateway instance. |
| Cluster ID | cluster | Cluster identifier (integer). Use 0 for single-gateway setups. |
| Description | description | Optional description. |
¶ 2.1 Gateway JSON example
{
}
The Cron gateway has no protocol-specific configuration — all the logic is in the addresses.
¶ 3. Addresses
¶ 3.1 Address format — cron expressions
The address name is the cron expression. The standard cron format uses 5 fields:
┌───────────── minute (0-59)
│ ┌───────────── hour (0-23)
│ │ ┌───────────── day of month (1-31)
│ │ │ ┌───────────── month (1-12)
│ │ │ │ ┌───────────── day of week (0-7, 0 and 7 = Sunday)
│ │ │ │ │
* * * * *
¶ Special characters
| Character | Meaning | Example |
|---|---|---|
* |
Every value | * * * * * = every minute |
, |
Multiple values | 0,30 * * * * = at minute 0 and 30 |
- |
Range | 0 9-17 * * * = every hour from 9 to 17 |
/ |
Step | */5 * * * * = every 5 minutes |
¶ Predefined shortcuts
| Expression | Equivalent | Description |
|---|---|---|
@yearly / @annually |
0 0 1 1 * |
Once a year (January 1st, midnight) |
@monthly |
0 0 1 * * |
Once a month (1st day, midnight) |
@weekly |
0 0 * * 0 |
Once a week (Sunday, midnight) |
@daily |
0 0 * * * |
Once a day (midnight) |
@hourly |
0 * * * * |
Once an hour (at minute 0) |
¶ Common examples
| Cron expression | Schedule |
|---|---|
* * * * * |
Every minute |
*/5 * * * * |
Every 5 minutes |
*/15 * * * * |
Every 15 minutes |
0 * * * * |
Every hour (at minute 0) |
0 8 * * * |
Every day at 8:00 AM |
0 0 * * * |
Every day at midnight |
0 8 * * 1-5 |
Weekdays at 8:00 AM |
0 8,12,18 * * * |
Every day at 8 AM, noon, and 6 PM |
30 6 * * 1 |
Every Monday at 6:30 AM |
0 0 1 * * |
First day of every month at midnight |
0 0 1 1 * |
January 1st at midnight |
¶ 3.2 Address parameters
| Label | JSON Key | Description |
|---|---|---|
| Cron format | name | The cron expression defining the schedule (see section 3.1). |
| Value | value | The value emitted at each scheduled tick. Default: 1. Can be a number, a string, or a JSON object. Can also be a JavaScript function that receives the previous value and returns the new value. |
| Description | description | Optional description. |
The Value field is also editable directly in the grid column Cron value.
¶ 3.3 Dynamic values with functions
The Value field can be set to a JavaScript function for dynamic behavior. The function receives the previous value as argument and returns the new value:
function(previousValue) {
return (previousValue || 0) + 1;
}
This example creates an incrementing counter that increases by 1 at each cron tick.
¶ 3.4 Address properties
| Property | Value |
|---|---|
| Readable | No |
| Writable | Yes (writing changes the emitted value) |
| Routable | Yes |
| Loggable | Yes |
¶ 4. Use case examples
¶ 4.1 Periodic Modbus polling at specific times
Read energy meters every 15 minutes during business hours, and once per hour at night:
| Address | Value | Description |
|---|---|---|
*/15 8-18 * * 1-5 |
1 |
Weekdays 8-18h: every 15 min |
0 * * * * |
1 |
All other hours: every hour |
Route both → %M1 (type: read).
¶ 4.2 Daily CSV export via FTP
| Address | Value | Description |
|---|---|---|
0 0 * * * |
1 |
Every day at midnight |
Route → $triggerExport (Internal address) → route to CSV driver export trigger.
¶ 4.3 Weekend/weekday HVAC schedule
| Address | Value | Description |
|---|---|---|
0 7 * * 1-5 |
21 |
Weekdays 7 AM: comfort mode |
0 19 * * 1-5 |
18 |
Weekdays 7 PM: eco mode |
0 9 * * 6-7 |
20 |
Weekends 9 AM: comfort mode |
0 22 * * 6-7 |
16 |
Weekends 10 PM: eco mode |
Route all → %bac:local/analogValue:1 (BACnet setpoint).
¶ 5. Developer reference
| Property | Value |
|---|---|
| Address regex | Standard cron (5-7 fields), @yearly, @monthly, @weekly, @daily, @hourly, @reboot, or @every <duration> |
| Readable | No |
| Writable | Yes (the address name must match the cron regex) |
| Events | Emits newValue on each cron tick with the configured json.value |
¶ Dynamic value function
The json.value field can be a JavaScript function receiving the previous value:
// Incrementing counter
function(previousValue) {
return (previousValue || 0) + 1;
}
// Toggle between 0 and 1
function(prev) {
return prev ? 0 : 1;
}
If json.value is undefined or null, the emitted value defaults to 1.
¶ Notes
- No
driverMethods.read— the driver is purely event-driven - CronJob is recreated on every address insert/update
- The address name IS the cron expression (not a human-readable name)