Can I use the TLC5940 LED Driver if I'm already using other SPI devices on my Arduino mega?

Question

The way I understand SPI is that 3 wires are shared (MOSI, MISO, & SCHK). The slave select is pulled high when you want to write to a specific device. The 3 shared wires can be daisy chained. The TLC5940 LED Driver says that it uses SPI but I don't see any documentation about a slave select. Can I just include this in the standard daisy chaining and assign a new slave select? In some forums online some people seem to indicate you can't use the TLC5940 on the same SPI bus as other devices. I thought that was the whole point of SPI. Are there different forms of SPI? I'm quite confused, can I use the TLC5940 with other SPI devices?

Answer 1

Can I just include this in the standard daisy chaining and assign a new slave select?

SPI is normally used as a parallel bus and requires MISO to be tri-state (disconnected when not selected).

In some forums online some people seem to indicate you can't use the TLC5940 on the same SPI bus as other devices.

The device does not have a chip select which gives a challenge. No direct wiring is possible but can be solved.

Are there different forms of SPI? I'm quite confused, can I use the TLC5940 with other SPI devices?

It is possible to connect the TLC5940 but it requires some extra logic. You can for instance block the clock signal when it is not selected. This can be done with a MOSFET or 74HC125 and a pull-low resistor.

Cheers!