sprintf not working

[E_Blue]

I'm trying to add text to a string buffer

[Ttelmah]

sprintf, expects to receive a _pointer_ to where the data is meant to go. So (for instance) USB_TxBuffer.

USB_TxBuffer[offsetX] is not a pointer. It's the value contained 'at' OffsetX inside the array USB_TxBuffer.
If you want to print 'to' the location 'offsetX' in the buffer you need:

&USB_TxBuffer[offsetX]

or

USB_Txbuffer+offsetX

[E_Blue]

Thanks for your fast and clear answer.

I understand what you just explain but Why if I just write USB_TxBuffer it works ok and write starting at the very first byte of USB_TxBuffer?

Should I use &USB_TxBuffer instead when I want to write the string starting at offset zero?
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Electric Blue

[Ttelmah]

No.

In 'C', the name of an array (with no brackets or index), is the pointer to it. It's a standard feature of the language. So USB_TxBuffer, is equivalent to &USB_TxBuffer[0].

[E_Blue]

Thanks, clear as clean water.
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Electric Blue