MCP23S17 SPI demultiplexing testing notes

Now I am doing SPI demultiplexing test.  The setup is summarized below.

1. RPi JTAG, PWM/CLK, SPI (with CE0, CE1) go to bread board at middle front.

2. SPI with CE0 go to MCP23S17 which is set to 16 pins output GA0~7, GB0~7.

3. MCP23S17 GA0~3 go to input of HC137 (3V0), HC137 output go to bread board (D)

4. MCP23S17 GB0~3 go to input of HC137 (5V0), HC137 output go to bread bread (E)

5. GPi wth 4 digit LED SPI Gnd, SCLK, MOSI, MISO go to C, CE goes to HC137 (3v3) output Y0.

6. EEPROM #1 SPI Gnd, SCLK, MOSI, MISO go to C, CE goes to HC137 (3v3) output Y1.

7. EEPROM #2 SPI Gnd, SCLK, MOSI, MISO go to C, CE goes to HC137 (3v3) output Y2.

Next step is test 3 SPI devices GPi, EEPROM #1, and EEPROM #2 in time sequence, using MCP23S17 to do the demultiplexing.

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