This is a very early port of MiSTeryNano to the Efinix T20BGA256 development board, allowing it to run Atari ST software like the game Spherical.
A custom add-on board for the t20bga256 is available here. This combines all the hardware into one somewhat robust setup.
The setup requires some additional hardware to be connected to the BANK1B_1C
connector. The photo below shows the HDMI being connected using an iCESugar
HDMI PMOD. The SD card is barely visible under the colored ribbon cable
and a Raspberry Pi Pico is set up on a breadboard as the FPGA companion.
It uses an additional USB connection with a USB hub to control wireless
USB receivers for keyboard, touchpad and game pad.
There's now also a dedicated hardware add-on to ease the setup.
An HDMI connector using 100nF capacitors in series with each TMDS line. Some screens also need 5V to be supplied. It's thus preferred to use a generic HDMI PMOD that generates all necessary signals from its 3.3V and data connections.
| Signal | Pin |
|---|---|
| TMDS_CLOCK_P | GPIOL_11 |
| TMDS_CLOCK_N | GPIOL_12 |
| TMDS_DATA_0_P | GPIOL_13 |
| TMDS_DATA_0_N | GPIOL_14 |
| TMDS_DATA_1_P | GPIOL_15 |
| TMDS_DATA_1_N | GPIOL_16 |
| TMDS_DATA_2_P | GPIOL_17 |
| TMDS_DATA_2_N | GPIOL_18 |
A SD/TF card slot needs to be connected to using six 33 ohms series resistors for the data, command and clock lines.
| Signal | Pin |
|---|---|
| SD_DAT[0] | GPIOL_22 |
| SD_DAT[1] | GPIOL_21 |
| SD_DAT[2] | GPIOL_26 |
| SD_DAT[3] | GPIOL_25 |
| SD_CMD | GPIOL_24 |
| SD_CLK | GPIOL_23 |
And finally, an FPGA Companion is needed for USB and general system control via SPI.
| Signal | Pin |
|---|---|
| SPI_CLK | GPIOL_29 |
| SPI_MOSI | GPIOL_30 |
| SPI_MISO | GPIOL_27 |
| SPI_CS | GPIOL_28 |
| SD_INT | GPIOL_31 |
The T20 is used to 95% by this and a few limitations had to be implemented to achieve this.
- ACSI hard disk support is permanently disabled as it uses a vast amount of resources.
- Builds are unstable, and you might need to play with the
seedvalue to get a stable result - HDMI is generated by pure logic and without dedicated LVDS shifters or the like and the signal may not be accepted by all displays
The TOS operating system is executed from the 4MB SPI flash. The TOS operating system needs to be flashed to offset 1MB (0x100000 or 1048576) into the flash using either the Efinity programmer or openFPGAloader. The following command will flash the German TOS 1.04 operating system.
$ openFPGALoader -b trion_t20_bga256 --external-flash -o 0x100000 ./tos104de.img
An optional secondary TOS version might be flashed to offset 0x140000 to be selectable from the on-screen-display.