Interfacing STP16CPC26 Led Display Driver to NRF52832 via SPI

RE: Interfacing STP16CPC26 Led Display Driver to NRF52832 via SPI

Jørgen Holmefjord — Thu, 01 Dec 2016 12:22:28 GMT

The clock is controlled by the SPI driver, so you will have to edit this, or use the SPI interface directly if you want to run the clock outside the SPI transfer. In the datasheet it is specified: Every rising edge of the CLK signal, a new data on SDI pin is sampled. This data is loaded into the shift register, whereas a bit is shifted out from SDO. If you run the CLK signal longer, you will clock out the data loaded into the shift register on the SPI transfer, so I don't think this is a good idea until you have enabled the LE, if you want to avoid data loss. Can you get confirmation from STMicro that you need the clock to be running when setting the LE signal, and that you have to set the LE signal exactly at the 16th rising clock?

RE: Interfacing STP16CPC26 Led Display Driver to NRF52832 via SPI

Shalin — Wed, 30 Nov 2016 15:35:42 GMT

Hello Jorgen, Thanks for your prompt reply. I had already tried that approach, I am attaching an image from my scope.20161130_102845.jpg The Pink line is the data, the Yellow is the clock and the Blue line is the pulse I am sending on the LE line. As seen in the attachment, there is no clock pulse available when I want to send the LE pulse. Is there a way to do that.

Thanks, Shalin

RE: Interfacing STP16CPC26 Led Display Driver to NRF52832 via SPI

Jørgen Holmefjord — Wed, 30 Nov 2016 12:36:53 GMT

Hi,

From the datasheet it looks to me like the pulse on LE is not happening on the rising edge of the 16th clock cycle, but rather after the 16th rising edge of the clock. I think the point is that you should wait until the SPI transfer is complete before you send the latch pulse, to ensure that the correct data is present in the SPI shift register (you should get this confirmed by STMicro).

If you are using the SPI master driver, you will get a NRF_DRV_SPI_EVENT_DONE event when the SPI transfer is done. You can set the LE pulse in the event handler to latch the data after completion of the SPI transfer.

Best regards,

Jørgen