# Document history
<a name="elpg-history"></a>

The following table describes important changes to the AWS IoT ExpressLink Programmer's Guide starting with v1.0. We also update the documentation to address any errors found or feedback received.


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| Change | Description | Date | 
| --- | --- | --- | 
| version 1.2 | The following sections and tables were updated:+  [Table 1 - Error codes](elpg-commands.md#elpg-table1) - New error codes were introduced:   27 : BLE ERROR   28 : CONFIGURATION ERROR   <br />+  [Table 2 - Configuration Dictionary Persistent Keys](elpg-configuration-dictionary.md#elpg-table2) - Added new non-persistent configuration parameters:   BLECentral\#    BLEPeripheral    BLEGATT\#    <br />+  [Table 4 - ExpressLink event codes](elpg-event-handling.md#elpg-table4) - New BLE Events introduced. <br />+  [12 Bluetooth Low Energy](elpg-ble.md) - New BLE commands introduced.  | October 27, 2023 | 
| version 1.1.2 | The following sections and tables were updated:+  [Table 1 - Error codes](elpg-commands.md#elpg-table1)   Introduction of ERROR 26 INVALID CERTIFICATE.   <br />+  [Table 2 - Configuration Dictionary Persistent Keys](elpg-configuration-dictionary.md#elpg-table2)   'Version' now allows for a suffix (for example, 'X.Y.Z beta2').   OTACertificate is now write-only.   <br />+  [8 Over the Air Updates](elpg-ota-updates.md) (formerly Chapter 9)   [8.5 Module OTA signature verification](elpg-ota-updates.md#elpg-ota-signature-verification)   Underlined sentence requiring OTA Certificate pre-provisioning.   Reworded last sentence for clarity.     [8.6 Module OTA certificate updates](elpg-ota-updates.md#elpg-ota-certificate-updates)   OTACertificate is now write-only.   ERR26 is produced when a corrupted or otherwise invalid certificate is presented.     [8.10 Host OTA Signature Verification](elpg-ota-updates.md#elpg-hota-sig-verification)   [8.11 Host OTA certificate update](elpg-ota-updates.md#elpg-hota-cert-update)   [8.11.2 CONF? *{certificate} pem*   »Special certificate output formatting option«](elpg-ota-updates.md#elpg-ota-confq-command)   Special 'pem' qualifier is now case insensitive (for example, 'pem' \| 'PEM').     [8.11.3 CONF {certificate}=pem   »Special certificate input formatting option«](elpg-ota-updates.md#elpg-ota-conf-command)   Special 'pem' qualifier is now case insensitive (for example, 'pem' \| 'PEM').      | July 25, 2023 | 
| version 1.1.1 | The following sections were added:+  [9 AWS IoT Services](elpg-iot-services.md) <br />The following sections and tables were updated:+  [4.3 Delimiters and escaping](elpg-commands.md#elpg-delimiters) <br />+  [4.4 Maximum values](elpg-commands.md#elpg-max-values) <br />+  [Table 1 - Error codes](elpg-commands.md#elpg-table1) <br />+  [4.7.2 CONNECT   »Establish a connection to an AWS IoT Core Endpoint«](elpg-commands.md#elpg-connect-command) <br />+  [4.7.7 FACTORY\_RESET   »Request a factory reset of the ExpressLink module«](elpg-commands.md#elpg-factory-reset-command) <br />+  [5.1.7 SUBSCRIBE*[\#]*   »Subscribe to Topic\#«](elpg-messaging.md#elpg-subscribeh-command) <br />+  [5.1.8 UNSUBSCRIBE*[\#]*   »Unsubscribe from Topic\#«](elpg-messaging.md#elpg-unsubscribeh-command) <br />+  [Table 2 - Configuration Dictionary Persistent Keys](elpg-configuration-dictionary.md#elpg-table2.title) <br />+  [Table 3 - Configuration dictionary non-persistent keys](elpg-configuration-dictionary.md#elpg-table3) <br />+  [Table 4 - ExpressLink event codes](elpg-event-handling.md#elpg-table4) <br />+  [11 Provisioning](elpg-provisioning.md) <br />The following sections were removed:+  4.1.3 SEND *{topic} message*   »Publish msg on the specified topic« <br />+  6 Status dictionary <br />  note that subsequent sections were renumbered <br />+  9 Additional services  | November 17, 2022 | 
| version 1.0 | Initial release. | June 20, 2022 |