PCM Interface is a kind of standard build on the same principles as SPI. The SPI interface can handle the clocked bit-streams, but I2S can also handle the PCM encoding. In simple words I should be able to send/receive voice effortless – just need to get my head around register settings in STM32F405 which is…
I decided to replace ESP-12 with a Raspberry PI Zero W fitted on the back facing front. The PLC card is of the same height as the PI Zero Length, so this is perfect. Mountimng it on top was difficult due to the Ethernet connector sticking out +Â I had no space fr routing. I…
Choosing GSM modules is a pain, but I landed on SIM800/SIM808. The difference is that the later contains GPS for an additional 4.- USD. I was first tempted to save those, but decided that a GPS add a very nice function for anything that is mobile. At a price of ca 10.- USD this is…
This one have a lot of potential as we basically create a Raspberry PI Hat that is a PLC Module and contain SIM800/SIM808. It makes a lot of sence doing this as a RPI Hat because I need RPI to do the more advanced voice processing for speech services.
Using SIM800 allows me to connect sound to the MCU through SPI. This enables Speech, TTS, IVR services to be added later, as well as the option to create a mobile home phone central later.
I initially wanted SIM800C because it support voice calls and it does analogue voice. My first idea was to connect this to a ADC/DAC on the MCU for digital voice services, but this is a bit complicated and involve a digital to analogue to digital conversion that I would avoid. What I need is “digital…
I can use my Universal Communication Adapter to code most of what is on this card, so I am in no hurry to order this PCB. The fact is I miss package sizes, so I just need to sit & wait a little for now. I am however running out of space in front, so…
This makes use of the ULN2003 that can take 5-50V input and drive 0,5A. This simple chip allows for multiple PWM channels that can be used for anything from relays to small steppers. This draft suggest 5 stepper motors and a actuator. The connectors on this is a Challenge due to the available width.
This draft illustrate a PWM module based on the driver of the motor controller we made earlier. We use a concept of a gate driver and 2 x HEXFET to create a Half H-Bridge. We will need 10V+ due to the gate driver, but we only need 1-3A on this one. I think it is…
Double click on the picture to see the larger version … The SIM800C uses a 4V PSU that need to support 2A. All the circuitry on top is PSU related according to reference – I have removed some, but need to see the PCB layout before I consider the rest. Also, I am not sure…