Question: how does UART Image Transfer sent multiple packets

[ljunquera]

This is really informational. I'm new to this and needed a little help understanding how the UART Image Transfer sends multiple packets for the image. I followed the chain but don't see where it loops through the data to send.

ImageTransferModuleManager -> sendImage
ImageTransferModuleManager -> sendCommandWithCrc
ImageTransferModuleManager -> sendCommand
UartPacketManager -> sendEachPacketSequentially
BlePeripheral -> uartSendEachPacketSequentially
BlePeripheral -> uartSentPacket
BlePeripheral -> write

It seems like UartPacketManager -> sendEachPacketSequentially should do it but I only see:

    func sendEachPacketSequentially(blePeripheral: BlePeripheral, data: Data?, withResponseEveryPacketCount: Int, progress: ((Float)->Void)? = nil, completion: ((Error?) -> Void)? = nil) {
        sentBytes += Int64(data?.count ?? 0)
        blePeripheral.uartSendEachPacketSequentially(data: data, withResponseEveryPacketCount: withResponseEveryPacketCount, progress: progress, completion: completion)
    }

or

    func uartSendEachPacketSequentially(data: Data?, withResponseEveryPacketCount: Int,  progress: ((Float)->Void)? = nil, completion: ((Error?) -> Void)? = nil) {
        guard let data = data else { completion?(nil); return }
        
        guard let uartTxCharacteristic = uartTxCharacteristic else {//}, let uartTxCharacteristicWriteType = uartTxCharacteristicWriteType else {
            DLog("Command Error: characteristic no longer valid")
            completion?(PeripheralUartError.invalidCharacteristic)
            return
        }
        
        isSendSequentiallyCancelled = false
        uartSentPacket(data: data, offset: 0, uartTxCharacteristic: uartTxCharacteristic, withResponseEveryPacketCount: withResponseEveryPacketCount, numPacketsRemainingForDelay: withResponseEveryPacketCount, progress: progress, completion: completion)
    }

I'm not seeing where you loop through the image data.

[antonio-openroad]

You are close to the answer. If you check inside uartSentPacket you will see that it splits the data and calls itself recursively until all the image data has been sent (or the process has been cancelled).

So to sent a new image:

• uartSendEachPacketSequentially calls uartSentPacket the image data and a starting offset of 0.

• uartSendPacket splits the data depending on the maximum transfer unit (MTU) negotiated with the peripheral and

calls write with that packet. When write finishes uartSendPacket calls itself recursively but with a new starting offset.

I hope this helps you