update readme

README.md

@@ -1 +1,30 @@
-# replace this
+# AWS IoT Core Thing with Certificate v3 construct
+
+This is a CDK construct that creates an AWS IoT Core Thing with a certificate and policy using [aws-sdk-js-v3](https://github.com/aws/aws-sdk-js-v3).
+
+Cloudformation does not support creating a certificate for an IoT Thing, so this construct uses the AWS SDK to create a certificate and attach it to the Thing.
+
+This construct is a modified version of this excellent [construct (cdk-iot-core-certificate)](https://github.com/devops-at-home/cdk-iot-core-certificates) to work with aws-sdk-js-v3.
+
+## Installation
+
+```bash
+npm i cdk-iot-core-certificate-v3
+```
+
+## Usage
+
+```typescript
+import { ThingWithCert } from 'cdk-iot-core-certificate-v3';
+
+const thing = new ThingWithCert(this, 'MyThing', {
+  thingName: 'MyThing',
+  saveToParamStore: true,
+  paramPrefix: 'test',
+});
+
+const thingArn = thing.thingArn;
+const certId = thing.certId;
+const certPem = thing.certPem;
+const privateKey = thing.privKey;
+```

src/index.ts

@@ -8,17 +8,51 @@ import { CfnParameter } from 'aws-cdk-lib/aws-ssm';
 import { Provider } from 'aws-cdk-lib/custom-resources';
 import { Construct } from 'constructs';
 
+/**
+ * Properties of ThingWithCert construct
+ */
 export interface ThingWithCertProps extends ResourceProps {
+  /**
+   * The name of the thing
+   */
   readonly thingName: string;
+
+  /**
+   * Whether to save the certificate and private key to AWS Systems Manager Parameter Store
+   */
   readonly saveToParamStore?: boolean;
+
+  /**
+   * The prefix for the parameter store path
+   */
   readonly paramPrefix?: string;
 }
 
+/**
+ * A CDK Construct for creating an AWS IoT Core thing with a certificate
+ */
 export class ThingWithCert extends Construct {
+
+  /**
+   * The ARN of the thing
+   */
   public readonly thingArn: string;
+
+  /**
+   * The ID of the certificate
+   */
   public readonly certId: string;
+
+  /**
+   * The certificate PEM
+   */
   public readonly certPem: string;
+
+  /**
+   * The private key
+   */
   public readonly privKey: string;
+
   constructor(scope: Construct, id: string, props: ThingWithCertProps) {
     super(scope, id);