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The mega UberGROM thread (start here)


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  • 8 months later...
On 7/23/2020 at 8:31 PM, globeron said:


(write up is maybe not 100%, but it might help other people)


I finally managed to get it to work

(if I remember correctly 2 years ago, I wanted to do this, because my nanoPEB RS232 did not work somehow)

and now with UberGromHDX I can transfer from a PC files via Serial to the NanoPEB (without taking out the CF-card)

but then came the TIPI (sidecar) in my life, but now I am building a network with multiple TIs and had a standalone

TI that needed to be networked (with a standalone 32K  or nanoPEB)


burn the ATMEL CHIP  (the .bin file eaprom_V_UG.bin) 

(I only programmed the ATMEL chip, in the past I wrote a procedure for this, see the last part)

UberCart-Programming-v1-Aug-2017.pdf 4.44 MB · 78 downloads



@F.G. Kaal  Fred:

It would be good to add a procedure the "how to" map the GROM base of the UART TTL device.



(my cable is USB-DB9 -- normal connector (MALE), to a DB9 (FEMALE) to DB9 (MALE) to the DB9 FEMALE UART device

and the pins are mapped like on your photo.  VCC to +5V,  TXD to TXD,  RXD to RXD, GND to GND)

(thus no need for a gender-changer or cross-cable-adapter).


To do the UART mapping:

1. Download the .zip here



2. as I use this on a standalone TI (with NanoPEB attached first, but actually want to use it with 32K attached only)

    how to get the file to the TI:

    a. Used the CF-card on my PC and saved the gromcfg.dsk to a volume on the CF-card

        (using the TIDIR tool of Fred  ti99-geek.nl website)

    b. then using the nanopeb  in TI-BASIC:  CALL MOUNT(2,Volume)

    c. with E/A  option 5 (of the UberGromHDX module) DSK2.GROMCFG


3. in GROMCFG now press CTRL F

    and browse with > to the   >983C

    then press A  (for >A000)

    then press U  (to assign UART)


4. then SAVE  (DSK2.UARTSAVE) 

    it overwrites the Ubergrom


5. press FCTN 7

    then make sure the CTRL B  (Base is ON), rest is OFF

    (not sure if this is correct, but it works for me)


6. Start TI99HDX 9.1  (settings are for me on COM3 for the USB port mapping)

    38400, 8, E, 1

    and at communication status DTR and RTS are on   (rest are all off)


7. start module > Editor Assembler V

    option 7 Utilities

    option 5 UberHDX

    it will initialise quickly and on the PC you will see also that it is initialized


    then for source enter SRC:  HDX1.










Selling this UberGrom + RS232 connection  https://www.ebay.com/itm/404526205864


See video for details

All components to connect a TI-99/4A UberGrom based  RS232 module to connect to PC (HDX Server) + cables 
* 1x  UberGrom + UART TTL RS232 module to connect to PC HDX Server software
* 1x USB-to-DB9
* 1x DB9 - DB9 Cable
Project (Website of Fred K.):
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