chipKIT Pi losing USB/Servial communication

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weclark
Posts: 1
Joined: Tue Nov 18, 2014 7:50 pm

chipKIT Pi losing USB/Servial communication

Post by weclark » Tue Nov 18, 2014 8:12 pm

I'm trying to replace an ATMega2560 with the chipKIT Pi. The problem is I am using the UART on the RPi to communicate to the chipKIT Pi. With the USB bootloader and a small program I can send/receive from USB (Serial) and UART (Serial1). When I load my program of ~64k things go bad. The USB interface disappears. I can see no good way to troubleshoot this as TX2/RX2 are also used by the ICSP interface. My project is a modification of the ArduinoPi Web-based interface by Jan Stevens.

kk6jr
Posts: 4
Joined: Thu Jan 15, 2015 6:22 pm

Re: chipKIT Pi losing USB/Servial communication

Post by kk6jr » Sun Jan 18, 2015 2:29 pm

weclark wrote:I'm trying to replace an ATMega2560 with the chipKIT Pi. The problem is I am using the UART on the RPi to communicate to the chipKIT Pi. With the USB bootloader and a small program I can send/receive from USB (Serial) and UART (Serial1). When I load my program of ~64k things go bad. The USB interface disappears. I can see no good way to troubleshoot this as TX2/RX2 are also used by the ICSP interface. My project is a modification of the ArduinoPi Web-based interface by Jan Stevens.
Having effectively only one serial connection between the chickpea and the Rpi is useless. A priority is to get another channel going. SPI is my choice.

My (related) question - when connecting SPI output from chickpea (my affectionate term for awkward ChipKIT Pi) to RPi is it really necessary to use a level converter (74LVC245 or similar). And if it is then why the heck was one not already loaded on the chickpea product?
Or are level converters not needed and the chickpea only actually sources 3v3 on SPI wires when it gets its power from the RPi? Or is a simple forward biased diode (or two) sufficient to drop voltage when connecting a 5v0 output on the chickpea to a 3v3 input on the RPi?

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