FAQ

Which route should I use?

• Use GMPay for all new integrations.
• Use EPay-compatible redirect only when the upstream system expects an EPay-style cashier redirect.
• Do not build new integrations on /payments/epusdt/v1/order/create-transaction because that route is no longer registered in current source.

Where do pid and signing keys come from?

From the admin panel API key records. Each merchant has a pid and a matching secret_key.

Why does the GMPay config differ between environments?

Because GET /payments/gmpay/v1/config is computed from your own admin data.

Its data.supported_assets list depends on enabled chains, enabled chain tokens, and available wallet addresses in that environment.

Chain Settings

Does Tron require a special API key?

Yes. You must configure a TronGrid API key for Tron chain support. Without it the node requests will be rate-limited or rejected.

What protocol should I use for each chain's RPC URL?

• Tron and Solana (SOL): use an HTTP/HTTPS endpoint.
• All other chains (e.g. ETH, BSC, Polygon …): use a WSS (WebSocket) endpoint.

Setting the wrong protocol will silently prevent transaction monitoring from working.

Exchange Rate Settings

The system uses an exchange rate API to convert fiat amounts to crypto equivalents.

Which exchange rate API is used?

The system can be configured to fetch rates from the community-provided Fawaz Ahmed Currency API.

API base URL:

https://cdn.jsdelivr.net/npm/@fawazahmed0/currency-api@latest/v1/currencies/

Example - fetch USDT rates:

https://cdn.jsdelivr.net/npm/@fawazahmed0/currency-api@latest/v1/currencies/usdt.json

Note: This is a community-maintained free API. Accuracy is not guaranteed. For production environments, consider using a paid exchange rate provider.

How do I configure the exchange rate API?

In the admin panel, go to Settings - Exchange Rate and enter your preferred API endpoint. The system will poll it periodically to keep rates up to date.

What happens if I leave forced rates empty?

Current releases seed rate.forced_rate_list with a built-in CNY stablecoin map:

{"cny":{"usdt":0.14705882352941177,"usdc":0.14705882352941177}}

If the forced-rate setting is deleted or saved as empty, Epusdt restores this built-in default. If you save any non-empty JSON map, Epusdt treats it as intentional and does not merge or overwrite it.

rate.api_url is optional. When it is set, it must be a public http:// or https:// URL.