DRV8308EVM: SPI Communication

Nolan Lee

Part Number: DRV8308EVM
Other Parts Discussed in Thread: DRV8308,

I am having some issues communicating with the DRV8308 on the DRV8308EVM. I want to be able to communicate with the DRV8308 via a SPI interface from a separate microcontroller rather than with the GUI. Currently I have pulled the jumpers and wired in MOSI MISO SCLK and SCS all from a separate micro controller directly to the EVM board. I have also jumped a 5V power to the RESET pin as well as have the jumper in place to pull SMODE LOW. I am unable to read from the 0x2A register which should return a value of 0x18.

Here are my signals.

over 6 years ago

0 Adam Sidelsky over 6 years ago

TI__Guru 65220 points

Nolan,

Could you explain the issue you're seeing?

What is the intention with the three transactions above?

Regards,

-Adam

0 Nolan Lee over 6 years ago in reply to Adam Sidelsky

Prodigy 70 points

Hey Adam, the top is the clk middle is MOSI and bottom is SCS. The intention is to read from the DRV8308EVM board at register 2A. From what I've gathered reading the datasheet, the first bit should be set HIGH to tell the DRV8308 that we are reading from it and the following 7 bits are the register address. Sending this signal I am not getting anything back from the DRV8308 from MISO.

0 Adam Sidelsky over 6 years ago in reply to Nolan Lee

TI__Guru 65220 points

Nolan,

You are correct in sending 0xAA, this is is 0x2A but with the WRITE bit HIGH.

What's the purpose for sending 0xAF twice after sending the address? In a write operation the data should be left off.

Regards,

-Adam

0 Nolan Lee over 6 years ago in reply to Adam Sidelsky

Prodigy 70 points

Hey Adam,

The following two are because the micro controller being used, the PIC32, shares a buffer for sending and receiving and shifts the data seen on the MISO pin into the buffer after a transmit has occurred. Therefore to receive data in the buffer, a “dummy” byte must be sent which is what the 0xAF is.

Nolan

0 Adam Sidelsky over 6 years ago in reply to Nolan Lee

TI__Guru 65220 points

Nolan,

What data are you seeing?

Have you checked if there is a pull-up resistor missing or similar?

Regards,

-Adam

0 Adam Sidelsky over 6 years ago in reply to Adam Sidelsky

TI__Guru 65220 points

Nolan,

I will close this thread due to inactivity, please post again if you have further questions.

Regards,

-Adam

0 Nolan Lee over 6 years ago in reply to Adam Sidelsky

Prodigy 70 points

Sorry for the delay. I believe the EVM board should be directly plug and play. I will try to add a pull up and provide an update.

0 Adam Sidelsky over 6 years ago in reply to Nolan Lee

TI__Guru 65220 points

Nolan,

It is Plug and Play as we have designed it. When you use it with a different MCU or modify the board, this can change.

Regards,

-Adam

0 Adam Sidelsky over 6 years ago in reply to Adam Sidelsky

TI__Guru 65220 points

Nolan,

Did you get the issue resolved?

Regards,

-Adam

0 Nolan Lee over 6 years ago in reply to Adam Sidelsky

Prodigy 70 points

Hey Adam,

So I currently am running the GUI provided by TI and probing each element, SCK, SCS, SDATO, and SDATI. I've found that an external pull up resistor is not necessary. The data coming from SDATO on the EVM board is the same as the data coming from SDATO when hooked up to a pull up resistor.
I am hoping to resolve this issue some time this week.

Best,
Nolan

0 Adam Sidelsky over 6 years ago in reply to Nolan Lee

TI__Guru 65220 points

Nolan,

Have you yet been able to get the correct data from the SPI interface without your modifications, basically using the EVM as it was sent to you.

Regards,

-Adam

0 Nolan Lee over 6 years ago in reply to Nolan Lee

Prodigy 70 points

Hey Adam,

After probing the EVM board, it seems like all my SPI signals are the same. Is there anything else I will need to supply to the DRV8308 via the EVM board other than the SPI signals?

Nolan

0 Adam Sidelsky over 6 years ago in reply to Nolan Lee

TI__Guru 65220 points

Nolan,

If the SPI signals are the same, is it an MCU issue?

Regards,

-Adam

0 Nolan Lee over 6 years ago in reply to Adam Sidelsky

Prodigy 70 points

Hey Adam,
I am using a microchip MCU part of the pic32 family. I am not sure where the issue would arise if it were a MCU issue.
Nolan

0 Adam Sidelsky over 6 years ago in reply to Nolan Lee

TI__Guru 65220 points

Nolan,

This could be several things:

1. MCU VIH/VIL/VOH/VOL mismatch.
2. GPIO pin is not configured correctly.
3. Code/software issue.

Regards,

-Adam

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DRV8308EVM: SPI Communication