Correct way to pull up/down RST

Discussion about the ZBasic language including the System Library. If you're not sure where to post your message, do it here. However, do not make test posts here; that's the purpose of the Sandbox.
Post Reply
FFMan
Posts: 502
Joined: 09 January 2010, 12:52 PM

Correct way to pull up/down RST

Post by FFMan »

The zx40N based project will only start when the USB lead is plugged in.

The USB adapter is permanently wired to the ZX40. Is there a recommended way to tie RST to prevent this behaviour or will I have to disc RST when not loading ?
dkinzer
Site Admin
Posts: 3120
Joined: 03 September 2005, 13:53 PM
Location: Portland, OR

Re: Correct way to pull up/down RST

Post by dkinzer »

FFMan wrote:Is there a recommended way to tie RST to prevent this behaviour [...]?
I'm not sure that I fully understand the issue but I gather that when the USB cable is not connected to the USB adapter the reset line is being pulled low somehow by the USB adapter.

It may be beneficial to connect the reset signal from the USB adapter to the reset line of the ZX-40n through a diode (anode to the ZX reset, cathode to the USB reset). Although the AVR devices have an internal pull up on the reset input, it still may be advisable to employ an external pull up, perhaps 10K or so.
- Don Kinzer
FFMan
Posts: 502
Joined: 09 January 2010, 12:52 PM

Post by FFMan »

i recall i had this issue before with a permanently connected USB.

I put a hidden switch on RST which fixed it.

thanks
Post Reply