USB to TTL cable connection

michaelherrera

I'm trying to connect the VOXL2 to a USB using a TTL to USB serial converter like this:
https://ftdichip.com/products/ttl-232rg-vreg1v8-we/
I was planning on using J3 pins 27 & 29 as RX & TX. Do you know what pins would work for the "Clear to send control input/ handshake signal" and the "Request to send control output/ handshake signal"? Would any GPIO pin be acceptable?

modaltb

Hi @michaelherrera ,

You don't need to use the RTS/CTS pins (we never do) so you can leave those unplugged.

But, that UART on pins 27/29 is only enabled in the debug kernel build (which takes about 2 minutes to bootup and offers a login prompt, but needs to be generated by yourself using the build guide )

Another option:

From https://docs.modalai.com/voxl2-connectors/#j3-pin-out:

Pin
3 GPIO_23_UART7_RXD, /dev/ttyHS1
5 GPIO_23_UART7_TXD, /dev/ttyHS1 (edited since first post... thanks Vinny!)

Those pins get to an UART that you can access from linux (/dev/ttyHS1) in the standard build.

So depending on what you need, the 1.8V TTL is correct for these UARTs, and you can omit RTS/CTS for flow control.

Vinny

@modaltb said in USB to TTL cable connection:

Pin
3 GPIO_23_UART7_RXD, /dev/ttyHS1
5 GPIO_23_UART7_RXD, /dev/ttyHS1

Pin 5 is TXD (Output).

Also note, each of the signals from the J3 connector is 1.8V CMOS levels.
If you are using an FTDI device, you can provide it with the 1.8V reference voltage from pin 47, and any one of the GND pins noted in the connector spec page.

michaelherrera

This was very helpful, thank you!