throbscottle
Well-Known Member
I keep going back to study the original jdm programmer design because it's so clever. But there are a couple of questions I have. I'm building my own usb variant (with boost converter to get vpp) and want to maximise the chances of it working! I'm using a cp2101 usb to uart bridge dongle. I'll post diagram when I finally get to test it.
I refer to the diagrams here https://www.electro-tech-online.com/threads/jdm-for-16f84a-20i-p-and-16f874-20i-p.3005/ because jdm.homepage.dk seems to have disappeared.
I know txd is used to generate the power, but I've seen references to reading back from the chip via the programmer. So is txd controlled by the software to turn off in order to read (and the 5v then just comes from caps?)?
In jdm3 an extra output is added to dsr. What is this for? Does it tell the software that the programmer is powered up?
I've looked at quite a lot of variants, with various resistor values between cts and dtr, or just a short. Where present, what is this resistor for?
I've connected cts straight to dtr since it looks like the resistor is related to rs232 voltage levels. Same goes for Q2.
I refer to the diagrams here https://www.electro-tech-online.com/threads/jdm-for-16f84a-20i-p-and-16f874-20i-p.3005/ because jdm.homepage.dk seems to have disappeared.
I know txd is used to generate the power, but I've seen references to reading back from the chip via the programmer. So is txd controlled by the software to turn off in order to read (and the 5v then just comes from caps?)?
In jdm3 an extra output is added to dsr. What is this for? Does it tell the software that the programmer is powered up?
I've looked at quite a lot of variants, with various resistor values between cts and dtr, or just a short. Where present, what is this resistor for?
I've connected cts straight to dtr since it looks like the resistor is related to rs232 voltage levels. Same goes for Q2.