Interfacing PSoC 4 Pioneer Board to 5V System

Question

I'd like to interface a Pioneer board to a 5V system. The system would also provide 5V power to the Pioneer board and the digital interface signals would all be at 5V (TTL) levels. After reading the Pioneer Kit Guide (specifically section 4.3.3), it's still not clear whether I'd feed 5V power in at J1-01, J6, or J11 (VIN), and whether that would permit 5V signals at the PSoC 4's pins.

johnbeetem · Answer

Since nobody has answered this, I'll take a stab at it. This is JMO/YMMV with no warranty expressed or implied. According to my read of the PSoC 4 and PSoC 5LP data sheets, both PSoCs on the Pioneer board can be powered from 5V. If you power them from 5V, then you can have 5V signals at the I/O pins. However, I/O pins are not 5V tolerant if you are powering from 3.3V: never exceed VDD by more than 0.5V. From looking at the User Guide 4.3.3 and the schematics, here's my take: You don't want to use Vin (J11 or J1-1). Vin only goes to the 3.3V LDO regulator. Instead, you want to connect 5V to one of the VDD pins like P4_VDD (J1-7, J2-6), VTARG (J6-1), or P5LP_VDD (J7-1). VTARG is wired to VDD through R4, and P5LP_VDD is wired to VDD through R5. Make sure both are indeed populated. You'll need to set other jumpers carefully, such as J13 to connect VDD and P4_VDD, and remove J9 so that VDD is not connected to VBUS or V3.3. I think this is right, or at least close. But do check the schematics yourself, and before powering up do continuity checks to ensure that 5V is connected where it should be (you can check at the bypass caps) and that 5V is not shorted to 3.3V somewhere. I'd also recommend that before you connect any I/O, first power from to 3.3V to make sure PSoC is happy, and then 5V to see if it's still happy. Also be extra careful that 5V is connected before powering your external I/O: if your I/Os are hot with PSoC 5V unpowered, you can do damage.

Former Member · Answer

Hello, You can always power the VIN (J1-01 or J11) from a source of 5V-12V. Make sure to power the PSoC 4 at 5V if you are feeding the PSoC 4 I/Os at 5V (Jumper J9 at 5V position). -Ranjith