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Diy prop plug emulation using the ESP32? — Parallax Forums

Diy prop plug emulation using the ESP32?

shadoclawshadoclaw Posts: 10
in Propeller 1

I just ordered two propeller 1 40 pin chips and just now realized I don't have a way to program them.

When Chip designed the Prop 1, his vision included a way to program them via RS232. As we know, the commercial prop plug emulates this. So it stands to reason that one should be able to use an ESP32 as an in circuit programmer, in the same way one would use a prop plug: USART to pins P30 and P31, a gpio pin to pull Reset LOW when it needs to, a 3.3v and a ground connection. The Prop burns the image to the 64k EEPROM that is connected via iic on pins P28/29.

Has anyone else been working on this, or something similar?

Comments

  • iseriesiseries Posts: 1,533

    The prop plug is just a fancy serial device with added circuit to do the reset logic the P1 needs.

    The Parallax WX module is an EPS8266 but includes the fancy startup code needed to program the P1. it emulates the reset logic.

    You also need the crystal that is no longer sold to make the P1 work. They do sell a faster one though.

    I had timing issues trying to program it but one could skip the hole issue by just programming the EEPROM directly with the program needed.

    Mike

  • shadoclawshadoclaw Posts: 10

    Well, yeah.

    Crystal issue, I have some 10Mhz crystals I was planning to use, nothing fancy, just set the pll in the code to 8x instead of 16x.

    Basically it's the fancy reset timing that is setting this all back. I'll check the datasheet again (it's been a minute) and see if it specifies anything about the reset issue.

  • shadoclawshadoclaw Posts: 10

    I am waaaaaay overthinking this

    I have a P2 EVAL board. I should be able to use this as a passthrough to Flexprop to program the Prop 1s, yeah?

  • shadoclawshadoclaw Posts: 10

    Nevermind - was overthinking it. Checked the prop plug schematic and bashed something together- and took pictures! The ceramic cap under the board is a 100 nF cap and, as it turns out, is the special sauce of the reset pulse. LEDs are optional but pretty.

    Won't be able to test until Friday when my props come in, and I will post the code for the ESP32 later.

    Edit: file size for the pics is too large, will have to convert and post later.

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