SPI MISO Level too low

Hey there,

I’m working with the HiFive1 Rev B Dev Board and want to add an external AD-converter via SPI. I use the breakout board ADC Click from mikroe with the MCP3204 (here is the schmatic: https://download.mikroe.com/documents/add-on-boards/click/adc/adc-click-schematic.pdf)
But now I have a problem with the MISO level (see the following picture).

CH2: CS0

The level of the MISO doesn’t reach the high level. If I disconnect the pin from the dev board, it reaches the 3.3V. My assumption was that the onboard ESP32, which is also connected to SPI, is not switching the MISO pin to high impedance. However, the CS2 pin is deasserted.

Does anyone have an idea what the error may be?

Hi - can you describe a little more detail about how you connected the ADC click board to the HiFive1 board? For example HiFive1-JX pin Y <–> ADC click board pin Z. The would help figure out if somehow the SPI pins are mismatched.

Hi David,

I have connected the pins as follows:

CS: HiFive1-J3 pin 3 (GPIO 2) <–> ADC click board pin 3 (CS)
MOSI: HiFive1-J3 pin 4 (GPIO 3) <–> ADC click board pin 6 (SDI)
MISO: HiFive1-J3 pin 5 (GPIO 4) <–> ADC click board pin 5 (SDO)
SCK: HiFive1-J3 pin 6 (GPIO 5) <–> ADC click board pin 5 (SCK)
3V3: HiFive1-J6 pin 4 <–> ADC click board pin 7 (+3.3V)
GND: HiFive1-J6 pin 6 <–> ADC click board pin 8 (GND)

I am sure that the connection of the ADC Click is correct.

I measured a current of ~35 mA flowing into the ESP32 MISO pin.
I don’t need the ESP32, so I took the the “quick and dirty” solution and disconnected it.
Now the problem is solved.

I having this issue with the MCP3008, after struggling with the CS pin. I have moved on with the AD7731, but I am even having issues with that reading from its registers.