First time poster here. Before I begin, I shall offer up a little background info first. Was an apprentice maintenance engineer until 2011, studied operational engineering degree until graduating this year with honours. Keen interest in engineering, mechanics and electronics. Have run own ebay business since 2011 selling electronic components whilst finishing my degree. I shall not however mention the business name as I'm fairly sure it'll be against terms of the forums.
The issue I would like a little help with is regarding a new stock item that turned up today that I've been testing. It's a USB to serial adapter with a CH340G chip on board. Drivers installed flawlessly and suffice to say I've been reasonably pleased with it.
I've performed a loopback test on itself and also communicated between a PL2303HXA adapter also without any issue.
There is a couple of issues when attempting to download to an arduino whether it be an UNO, Nano or Mini pro.
Before anyone mentions it, I'm aware that the chip has the ability to switch between TTL and RS232 modes. This is determined by the RS232 pin. The internal pulldown resistor (as it is on the board) means that the serial lines idle high
The adapter itself seems to pull the reset line low, raise it and then hold it back at low. Even with the reset line disconnected and performing a manual reset, the adapter doesn't even make an attempt to transmit anything. If I watch the Tx line of the adapter with my scope, it doesn't pull low at all i.e. I don't see a start bit. If I used the PL2303 in the same scenario, I see the start bit and the rest of the data.
It is a little barmy because I can communicate with the arduino using the CH340G board, send and receive, it just won't download a program.
It's frustrating because I purchased 30 of these boards in order to be able to provide an alternative to expensive FTDI, lacking PL2303 and unpredictable CP2102 boards for programming the Mini Pro's so any help will be appreciated.