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January 12, 2012
I am a semi-retired software engineer (30+ years) delving into robotics for fun. My other hobbies are Cruising and Photography. I have a photo oriented web site at www.garycamp.com .
about 3 years ago
Is this item discontinued? What’s up with can not be backordered?
about 3 years ago
6/29/2012, I did not have the missing ACK problem TimWhite experienced but my SNAP RF100 failed to respond to the i2cRead called on the HMC6352. After incorrectly assuming it might be SDA/SCL levels, I finally fixed my problem by increasing the i2cRead function’s ‘retries’ argument to 10. I did not characterize the exact number of retries that will work, I just tried 1 and 4 which both failed, then 20 which worked and then 10 which worked. FYI, I do a 10ms delay between the i2cWrite to the HMC6352 to request it read the heading and the i2cRead to read the HMC6352’s response. The HMC6352 datasheet says it takes 6ms to get the heading but I just used a state machine with a 10ms hook to synchronize the i2cWrite and i2cRead.
I also tried the HMC6352 BOB with a SNAP RF100 (3.3v) micro and had I2C read problems. I then used it fine with a BasicMicro Nano 18 (5.0v) micro and never determined the problem. I just tried the HMC6352 BOB with a Parallax Propeller QuickStart board (3.3v) and it failed. So I connected the Propeller (3.3v) to the HMC6352 BOB (5.0v) via a BOB-08745 Level Converter using the two Tx bi-directional interfaces for SDA and SCL and it worked fine (compass must be on a jumper away from the breadboard). I retried the SNAP RF100 (3.3v) micro and got it to work with and without the level converter by increasing the i2cRead function’s ‘retries’ argument to 10. I did not characterize the exact number of retries that will work. I went back to the Propeller, using a logic analyzer this time, and determined that the HMC6352 object that I was using put the 6ms delay in the wrong location (between sending the $43 Read and reading the 2 byte heading on the I2C bus). The Propeller worked fine with 3.3v and no level converter after I moved the delay. Go figure :) I’ve revised this comment several times and this is my last since I now have successfully used the HMC6352 with a BasicMicro Nano18 (5.0v), Synapse SNAP RF100 (3.3v) and Parallax Propeller QuickStart (3.3v w/o level converter and 5.0V w/level converter).
I connected the SOMO-14D to a Parallax Propeller QuickStart board then wrote my first Propeller program to operate the SOMO-14D using the serial mode documented in the datasheet. I used a 2GB microSD card from Best Buy and the demo AD4 files provided at the 4D Systems web site. Everything worked on the first try (I’m a 30 yr programming veteran and things rarely work the first try ;-). Really cool. I checked in the Propeller code at the Parallax Propeller Object Exchange. It includes a menu based demo program to exercise the various SOMO-14D features. This was a great first Propeller project and again, the SOMO-14D worked as advertised.
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