Propeller 1 with MCP2221a not detected on COM port

ieatsoupwithafork

Hey all,

I'm pretty new to the Propeller and I'm trying to piece together a simple board with a propeller and MCP2221A USB to UART/I2C converter. I've wired it on a breadboard with all the necessary connections and checked voltages with a multimeter. For the life of me I can't get my windows machine to detect the Propeller. It shows up as COM7 but downloading code always fails.

The MCP2221A doesn't have a "reset trigger" signal so I manually ground the reset pin on the propeller low when uploading, yet it still doesn't work.

If anyone can point me in the right direction that would be great.

Thanks!

jmg

@ieatsoupwithafork said:
I'm pretty new to the Propeller and I'm trying to piece together a simple board with a propeller and MCP2221A USB to UART/I2C converter. ... The MCP2221A doesn't have a "reset trigger" signal

Why choose such a primitive and slow UART part, when it only makes life more difficult ?

ieatsoupwithafork

@jmg it was the only part available in DIP form, and I like prototyping with thru-hole parts.

jmg

@ieatsoupwithafork said:
@jmg it was the only part available in DIP form, and I like prototyping with thru-hole parts.

Ah...
You can get tiny modules from AliExpress with USB_UARTS mounted and USB connectors fitted.
Look for parts like CP2102N, CH9102, CH343, CH340, CH9340, PL2303GC, etc modules and choose one that is not too pin-starved. (ie has reset ability)

macca

@ieatsoupwithafork said:
The MCP2221A doesn't have a "reset trigger" signal so I manually ground the reset pin on the propeller low when uploading, yet it still doesn't work.

That's the reason: the upload protocol has precise timing, I don't think you can start the upload at the precise time after reset (milliseconds, not seconds...).
Unless it is possible to assign DTR to an output pin, I don't think that part is usable in this context.

@ieatsoupwithafork said:
it was the only part available in DIP form, and I like prototyping with thru-hole parts.

If you have a PIC18F14K50, I wrote a USB-Serial firmware here specifically for a P1 prototype board:
https://github.com/maccasoft/propeller-dev-firmware
It is basically the cdc_basic sample from Microchip MLA with some changes, I think it can be easily converted to other parts.

Wuerfel_21

@macca said:

@ieatsoupwithafork said:
The MCP2221A doesn't have a "reset trigger" signal so I manually ground the reset pin on the propeller low when uploading, yet it still doesn't work.

That's the reason: the upload protocol has precise timing, I don't think you can start the upload at the precise time after reset (milliseconds, not seconds...).

You actually can, it's not that precise. I used to be able to do it with ~80% accuracy. You have to hold in your reset button, start the compile/upload, then release it at the right time.