"iOS app developers do not need to join the MFi Program. Everything app developers need is in the External Accessory Framework" https://developer.apple.com/docu

"iOS app developers do not need to join the MFi Program. Everything app developers need is in the External Accessory Framework" https://developer.apple.com/documentation/externalaccessory/easession https://developer.apple.com/documentation/externalaccessory/... Technically there is a serial cable you can buy for hobbyist/personal/internal use but "Under current Apple policy this cable may not be used with apps sold on the App Store." https://redpark.myshopify.com/products/serial-cable-l2-db9v https://redpark.myshopify.com/products/serial-cable-l2-db9v