AVR and CC3000

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minerva
 
Posts: 58
Joined: Sun Dec 06, 2009 11:12 pm

AVR and CC3000

Post by minerva »

The attached schematic is a basic custom board combining an ATmega328 and a TI CC3000.

It doesn't work. It just sits there at "Initialising the CC3000 ..." in the serial monitor and doesn't get past that.

I'd like to know if anyone has any ideas as to why it might not be working. Thanks in advance! :)

To remove the need for level translation components, the microcontroller is run at 3.3V, and a 8 MHz crystal is used so that the AVR is running with its crystal oscillator inside the officially supported voltage spec.

It might be helpful if I had the schematics for the Adafruit boards, but as far as I can tell those are not up on GitHub yet.

The 3.3V LDO used is rated for 500mA output, which should be plenty for the CC3000.
5V is supplied into the board to the 5V rail, although this is not shown on the schematic.

Everything should be basically consistent with the TI CC3000 schematic checklist.
For test purposes I'm using the Adafruit CC3000 library code and "buildtest" example program.

CC3000 Int, CC3000 En and CC3000 CS are pins 3, 5 and 10 respectively (in the Arduino numbering) so it's exactly the same as the Adafruit shield and these are left unchanged in the code.

The only thing changed in the code is the SSID, password and security type obviously. The same code, same WiFi AP, same network, same settings, same conditions, and same distance to the access point, are confirmed to work successfully using an Adafruit CC3000 shield.

The board is only sitting about 3 feet away from the WiFi access point.

There is no SD card in the card socket, so there is no possible issue with the SPI devices not going tristate properly. The CC3000 is the only SPI device and it doesn't have to share with other devices that may not be relinquishing the bus properly.

The AVR is programmed with the Arduino bootloader, configured as a Arduino Pro Mini Atmega328 3.3V 8MHz.

For the sake of simplicity, the CC3000 I2C lines are hard-wired together without 0-ohm resistors, the CC3000 test UART breakout pins are not broken out, the reserved pins are not broken out.

The antenna has been changed slightly... it's a microstrip meandered inverted-F 2.4 GHz antenna as per TI AN043. The matching/HPF components are kept unchanged as per the datasheet reference values.

IF there is an issue with antenna gain or improper impedance matching or something I would still expect it to have enough link budget to work sitting a couple of feet away from the AP.

When new CC3000 silicon is purchased, does it require any special firmware configuration before use?
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