After doing a fair amount of breadboarding during the last few lab sessions, I decided to stop and try to sketch out what it is exactly I’m trying to achieve in the design. Due to the fact that it can take a few attempts to get a circuit design correct, I decided to mock it up digitally in Eagle rather than sketch it out by hand. This proved to be a good opportunity for me to recap on a Sparkfun Eagle tutorial I followed part way through last week. I was surprised by how much I had forgotten since last week which served as a reminder of the importance of regular practice in the use of any tool. After some trial and error I managed to draw out a simplified schematic design which allows a modular approach in regard to the interface controls. My intention is that the user will be able to choose the type of controls they would like to use for controlling the parameters of the ISD1820. The user will be able to pretty much design the interface themselves in a quick and convenient manner. In order to achieve this I’ve deployed several ATTiny85 IC’s in the design, a side affect of this is that the BOM cost is starting to grow quite significantly. Perhaps once I’ve gained a bit more knowledge of electronics I’ll be able to design a lower cost alternative.
I found that some common components were not included in the Eagle default library. There is however a fantastic online resource of free Eagle libraries from diymodules.org which proved to be quite useful. So far I’ve created designs for four modular controls, which are listed below along with links to the online resources the designs are based upon.
As each of the modular controls is dependent on an ATTiny85, an important next step is to develop and test the code which will run on each device. In addition to this I also need to implement a an L78L05 voltage regulator which will allow me to power the circuit from a 9V battery – and investigate ways in which the mic input can be cut when a mono jack is connected to the input.