877 I2C EEPROM Project Selection
877 : I2C EEPROM Project Selection
- Author: Uri Shaked
- Description: Prototype for reading the selected Tiny Tapeout design address from an I2C EEPROM
- GitHub repository
- Open in 3D viewer
- Clock: 20000000 Hz
How it works
This is a prototype for automatic project selection in Tiny Tapeout. It reads the design id from an I2C EEPROM and selects the corresponding project. The design id is stored in the first two bytes of the EEPROM memory as a big endian 16-bit number. The design id is then used to select the project by setting the ctrl_sel_inc signal to the lowest 10 bits of the design id.
The project also prints the 16-bit number read from the EEPROM to the UART port on uo_out[4] (baud rate 115200, 8N1) for debugging purposes.
The design also contains a ring oscillator that can be enabled by setting rosc_clk_en (ui_in[7]) to 1. The ring oscillator is used to generate a clock signal on the rosc_clk_out pin (uo_out[7]) that can be fed back to the clk input, so no external clock is needed.
The ring oscillator has 11 stages and a 5-bit divider. We estimate the frequency of the ring oscillator to be around 550 MHz, and the frequency of the divided clock to be around 17.2 MHz.
How to test
You need to connect a 1 kbit or 2 kbit I2C EEPROM (e.g. 24C01 or 24C02), program the selected Tiny Tapeout design address into the first two bytes of the EEPROM memory, and connect the EEPROM to the SCL/SDA pins with a 10k pull-up resistor. After connecting the EEPROM, reset the design, and and then observe the ctrl output pins to see if the design id is correctly read from the EEPROM:
ctrl_sel_rst_nshould go low, and then highctrl_sel_incshould pulse high according to the lowest 10 bits of the number stored in the EEPROMctrl_enashould go high
For more information about those signals, please refer to the Tiny Tapeout Multiplexer documentation.
You can clock the design externally with a 20 MHz clock signal, or enable the ring oscillator by setting rosc_clk_en to 1 and connect the rosc_clk_out pin to the clk input.
External hardware
I2C EEPROM (24C01 or 24C02) and two 10k pull-up resistors on SCL and SDA pins.
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | ctrl_sel_rst_n | SCL | |
| 1 | ctrl_sel_inc | SDA | |
| 2 | ctrl_ena | ||
| 3 | |||
| 4 | uart_tx | ||
| 5 | |||
| 6 | |||
| 7 | rosc_clk_en | rosc_clk_out |