Once a reader has been paired with a mobile device, you can begin authorizing cards.
Once an authorization response is received with the encoded payment method, indicate to the merchant that the transaction is complete.
Create a trigger in your mobile app to begin an authorization by calling the start transaction function. For instance, your trigger could be a “Pay Now” button for a server to ring up a table, which will run the auth function. Be sure to provide the required parameters for the start transaction function, listed in the Card Present SDK documentation.
On a successful response, the mobile card reader is ready to collect card information. Note that the call will timeout if a card is not provided after 60 seconds. It is recommended to display this pending status and the time window in your mobile app.
Mobile card readers can collect payment info from a card in the following ways:
- Using the chip (“dip”)
- Using the mag stripe (“swipe”)
- Using NFC (“tap”)
Most cards today have EMV chips. If an attempt is made to swipe an EMV chip card, the reader will reject the swipe and the Card Present SDK will prompt your app to ask the payer to dip the card instead. In case the chip is damaged, the reader will fallback to swipe mode after 3 consecutive failed dip attempts. Those 3 attempts and the subsequent dip must occur within the same Card Present SDK transaction (a single call to start the card reader).
Use Case: Complete 1 Transaction With 2 Cards
Oftentimes, customers will begin a payment with a gift card (or any other card with a balance limit) which does not have sufficient funds for the requested authorization amount. In these cases, a partial authorization will return, allowing the available balance on the card to be charged, but a remaining balance due.
Your platform should build out logic in your mobile app to handle splitting a single transaction into multiple payments to cover this use case.
To complete these kinds of transactions, prompt the merchant to run a second authorization for the remaining amount due.
You’ll now have 2 encoded payment methods, each to be used in seperate POST /payments requests for the authorized amounts. Take care to note the encoded payment method which returned with a partial authorization, and only capture the authorized amount via the API.
Note that the flat fee will be applied to each leg of the transaction, so these use cases are more expensive than completing a single transaction with a single card.
Chip cards are able to be coded differently by the issuing bank. Unlike mag stripes, the card reader can interrogate the chip and potentially reject a card for various reasons. These are the key business rules enforced by WePay and the Card Present SDK:
- Authorizations are always completed online, so internet access is always required to collect an authorization and then process a payment (internet access is also required for mag stripe transactions).
- Cards that are set to require a PIN cannot be accepted. Cards issued outside the US may be “PIN Preferring”, meaning that they have a PIN and require it if the reader supports it. However, the vast majority of these also allow “chip & signature” transactions, which is what is used in the US.
- An exception to the above exists with the Moby 5500; PIN preferring cards will largely be accepted by the Moby 5500, unless the card only accepts “chip & PIN” without the “chip & signature” fallback. Those cards will be declined, and the card holder should expect this. These cards are infrequent but are sometimes still issued by foreign banks or for cards with niche uses, such as health savings accounts.
- Cards must accept USD as a currency - this does not mean it has to be issued by a US bank. While WePay and the Card Present SDK both accept cards from anywhere in the world, not all cards are set to allow USD.
- Very rarely, a card network issues new cryptographic keys. When this happens, an update to the Card Present SDK is required. Authorizations attempted when an update is required will fail, and WePay will return an error in the Card Present SDK with the failed authorization delegate block. Call the firmware upgrade function in order to unblock the card reader from authorizing.
- In addition, cards can fail to process via the chip for the same reasons a magnetic stripe can fail, e.g. expired card.
Cards with chips can, and often do, have multiple “payment applications” on them. For example, there can be both a credit and a debit application. In most cases, the Card Present SDK is allowed to choose the credit application automatically. It is possible that the Card Present SDK won’t be able to choose, and when this happens the SDK makes a select EMV application callback to your mobile app to present the choice to the payer.
Your mobile app will need to collect certain details from the payer, depending on how the transaction is accomplished. For dip, swipe, and tap transactions you must collect the following in your mobile app:
- Signature (when applicable)
- NFC/contactless payments require signatures
- Merchants who accept tips are encouraged to collect signature
- Merchants who wish to validate the terms of sale (such as “all sales final”) are encouraged to collect signature
- Email address (optional)
The payer’s email address will not be passed to the Card Present SDK, but can be used in the POST /payments request, which we outline next.
After the manual or physical authorization flow has been initiated, the Card Present SDK then attempts to authorize the provided card information. The Card Present SDK will respond a Payment Info and an Authorization Info object, which both get passed back to the delegate method. There, you can identify whether the authorization succeeded or failed, and retrieve the encoded payment blob on a success:
|Payment method blob||
|Merchant receipt info|
|Payer receipt info|
|Offline? (boolean value)|
|EMV information (for receipts)|
Find the definitions of these results in the constants file of the Card Present SDK, and in the Classes section of the SDK documentation (found in the Card Present SDK package).
When the Card Present SDK responds with either approved or partially approved values for the authorization result, the transaction can be considered complete from the user perspective. Get the encoded payment method value from the payment info delegate and continue to the next article, Process Payments.
Next Up: Process Payments
Use encoded payment methods to process payments.
- Handle payment responses
- Leverage different capture flows
- Manage payment operations
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