SPIN Problems Using Non-Parallax USB to TTL RS-232 Adapter.
Duane C. Johnson
Posts: 955
Why won't my Spin recognize my USB to RS-232 Adapter.
Its on COM6.
TeraTerm, my terminal emulator, recognizes it.
I can communicate with DongleBasic running in the propeller.
I like this adapter because it has extra power output pins for 3.3V and 5V.
Does Spin require us to use only their adapter? (I have the Parallax unit.)
Duane
Its on COM6.
TeraTerm, my terminal emulator, recognizes it.
I can communicate with DongleBasic running in the propeller.
I like this adapter because it has extra power output pins for 3.3V and 5V.
Does Spin require us to use only their adapter? (I have the Parallax unit.)
Duane
Comments
Some work, and some don't. I had a Belkin that I spent a day trying to get it to work, to no avail. But I have a Keyspan USA-19HS that lives with the Propeller swimmingly.
Drivers I suppose.
We had some issues with this last year and Pullmoll did some very clever experiments with the timing of the pulses. The solution is to trigger on the negative rather than the positive edge. For the demo board, the solution was to swap an NPN transistor to a PNP transistor (we changed a BC547 to a BC557 but any small signal transistor will do). The dracblade board now has a BC557 and it seems to work well with a range of USB to serial adaptors, including a number of $1.99 ones from ebay.
There is another solution but it involves changing the timing in the proptool, and in BST and in Homespun, and after some discussion, this solution was rejected as there were some other unintended consequences.
There may be another solution changing values of the RC reset network, but it depends on which board you have.
Duane
These are quite plentiful on ebay and elsewhere for about $5.00us.
And several variations.
These are based on the Silabs CP2102.
I really like this adapter because it supplies both 5V and 3.3V from
the USB port.
I have found that the RST, reset, pin is not compatible with SPIN.
It represents a USB reset function.
What we need is a pulsed low when the DTR line goes high.
The CP2102 has this line, unconnected, on pin 28.
I used a 2N7000 MOSFET to invert and create the low going pulse.
Here is a crappy picture.
1. Remove the Via to the USB reset line on pin 9.
2. Form the leads on the 2N7000 and solder GND and the DTR on the CP2102.
3 Solder the .1uF capacitor between the smt resister and the 2N7000 Drain.
4. Solder a 4.7 KOhm resister between +3.3V and the 2N7000 Drain.
That's it.
This works on several versions of my homemade PropSticks.
Note! the pins are not in the same order as that of the Parallax unit
so either make a special cable or connector gender changer.
Have fun!
Duane