PentiumPC 119 Posted October 21, 2011 Author Share Posted October 21, 2011 Just found out HC05 cannot work without the Key tied to ground (Pin34). The diagram shows a the pin with a pull down resistor of 10K, but somehow 10K is too much for it to work. What will be a safe value for a pull down? The pin needs to be pulled high for the module to go into command mode. The other solution is to use a jumper and do away with the switch and resistor, since you only use the switch occasionally. Appreciate if anyone can give me some advise. Rregards, Terence Quote Link to post Share on other sites
RobG 1,892 Posted October 21, 2011 Share Posted October 21, 2011 Looks R5 the reason they used 10k. You can safely use 1k to pull the pin down and you can also add a parallel resistor to the switch. Then you populate only one you need. For master you would not need switch. What do you think? PentiumPC 1 Quote Link to post Share on other sites
PentiumPC 119 Posted October 22, 2011 Author Share Posted October 22, 2011 HI RobG, HC05 will need Pin34 high on power up to put it into AT Command mode for programming, in normal use it needs to be tied Low. So will a jumper be better? Looks R5 the reason they used 10k. You can safely use 1k to pull the pin down and you can also add a parallel resistor to the switch. Then you populate only one you need. For master you would not need switch. What do you think? Quote Link to post Share on other sites
RobG 1,892 Posted October 22, 2011 Share Posted October 22, 2011 I guess it depends on how often you will use it, for sporadic use jumper should be fine. PentiumPC 1 Quote Link to post Share on other sites
PentiumPC 119 Posted October 24, 2011 Author Share Posted October 24, 2011 decided to redo the whole board after all the comments and suggestions, learn more about PCB layout. Changes made. 1. Removed extra foot print for LED and use trace jumper instead, so you solder what you need to connect the status LED. 2. Moved Module above and use copper pour for GND plane, for better placement and EMI shielding. (I think ..haha) 3. PCB cut out so that the trace antenna in exposed. 4. moved LED to the bottom layer but place it at the edge, so we can still see the light from LED. here is capture of the brd. Quote Link to post Share on other sites
RobG 1,892 Posted October 24, 2011 Share Posted October 24, 2011 You can make RX/TX header smaller by doing this: Quote Link to post Share on other sites
PentiumPC 119 Posted October 24, 2011 Author Share Posted October 24, 2011 Hmm.. How do we switch TX/RX pin with this?? I am adding this in cause some MCU need to have Hardware UART pin switched on the LaunchPad. Please advise thanks. Hope to get it out soon. haha. Since I still have some space on the 50x50mm board, I am going to add a logic level translator, again can be broken of if not needed. Thinking of using TXB0104, don't know if I got the skills to make it work or not, maybe should just stick to this. Regards, Terence Quote Link to post Share on other sites
RobG 1,892 Posted October 24, 2011 Share Posted October 24, 2011 For straight through, jumpers are inserted horizontally, for switched, vertically. PentiumPC 1 Quote Link to post Share on other sites
PentiumPC 119 Posted October 24, 2011 Author Share Posted October 24, 2011 For straight through, jumpers are inserted horizontally, for switched, vertically. Oh yeah.. I am so blind.. Quote Link to post Share on other sites
PentiumPC 119 Posted October 25, 2011 Author Share Posted October 25, 2011 Final.. I will not try to stuff the board to 50x50mm. SugarAddict, bluehash and zeke 3 Quote Link to post Share on other sites
zeke 693 Posted October 25, 2011 Share Posted October 25, 2011 Nice board shape. :thumbup: Quote Link to post Share on other sites
PentiumPC 119 Posted October 26, 2011 Author Share Posted October 26, 2011 Out for production, will know if i screw up in 2 weeks time. Making this board is like rechecking the door over and over before getting out of the house. Regards, Terence. Quote Link to post Share on other sites
PentiumPC 119 Posted October 26, 2011 Author Share Posted October 26, 2011 Nice board shape. :thumbup: Will be nice with red solder mask.. then that is another $10.. haha. Quote Link to post Share on other sites
GeekDoc 226 Posted October 29, 2011 Share Posted October 29, 2011 Will be nice with red solder mask.. then that is another $10.. haha. Which fab did you use? Quote Link to post Share on other sites
PentiumPC 119 Posted October 30, 2011 Author Share Posted October 30, 2011 Will be nice with red solder mask.. then that is another $10.. haha. Which fab did you use? Seeed studio.. iTead's new color PCB service looks sweet.. will try that on my next design. Quote Link to post Share on other sites
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