mangOH Red Mediatek WiFi: Serial or SPI?

mangOH Red
1

I’m trying to put together a device using the mangOH Red platform (with a WP7702 module, if that part is important). My application (a GPS tracker with a display) needs USB, serial, and WiFi internally and a USB host externally. I’m trying to figure out if this is possible with the on board WiFi adapter.

As I understand it:

  • There’s one USB host (from the USB hub) going to the IOT connector and one to the external connector, so I’m good there.
  • The third goes to a USB->SPI->MediaTek interface so that doesn’t consume a serial port. However, it’s not clear whether this port is actually used?
  • There are two serial ports on the WP7702 module. One is the Linux console (which I would like to keep for debugging purposes). The other is mux’d with the IOT connector, the Raspberry Pi header, and the MediaTek.

The instructions I got (https://github.com/mangOH/mangOH/wiki/mangOH-Red-mt7697-WiFi) for getting the WiFi going seem to imply that the Serial port AND the SPI port are required for WiFi. Is that true?

Also, I get a lot of kernel OOPS()'s or PANIC’s when I have the driver loaded. I’m assuming that this is not yet supposed to work (which is a different frustration) and still is under development?

2

The best option is to use Serial and NOT SPI. SPI on MTK is too slow (<50kbps) while UART will give you close to 800kpbs data rate.

Driver should work and there should be no kernel panic issues if the github steps are followed properly.
Can you also check the google hangout we did on that opic?

3

Ok - it turned out I had both the serial and the SPI drivers loaded at once, which isn’t what I wanted. Loading just serial fixed the kernel panic’s. However, it is very unfortunate that the SPI is unusable. It should be a close to a 50 megabit connection over SPI. This is going to complicate my design as I no longer have a serial port available plus I have to power a USB to SPI converter that is useless… Ah, well.

4

Hey @fgodfrey,

We reached the same conclusion here when working on a new board design based on MangOH Red. If you want to flash the MT7697 from the target (you probably do since the MTK chip does not ship with firmware), you need to use a specific UART. The MT7697 has 2 UARTS, but one of them is used to “pin strap” the chip into firmware flashing mode. I can provide more details on this if you’re interested.

Cheers,
Nick

P.S Might be worth considering a UART switch to get some more I/O?

5

Thanks - unfortunately, I’m not doing my own board for this (this is a hobby project, not a full product and I only need one) so I’m stuck with whatever is on the mangOH. I can make it work, it’s just going to be more annoying than it needed to be (I’ll probably put in a board with a USB hub on it and an FTDI USB/Serial). A UART switch won’t help with the way the MangOH is laid out. I need to look into whether the CF3’s GPIOs can trigger interrupts since that + an I2C GPIO device will probably do what I need.