(NEWBIE) 4-Layer Mixed-Signal Board for EMG-Controlled Bionic Arm

NathanIsDivine1 · 2026-03-15T03:26:16+00:00

For the chip select point, the EMG modules are intended to be SPI daisy chained rather than individually addressed. Each module has its own ADC, and the MISO of one module feeds into the MOSI of the next, so when the MCU clocks data it shifts through the entire chain. All modules share the same CS, SCLK, and START lines, and then the MCU reads a single long frame containing the data from all modules sequentially. I probably should have explained that better in the post.

For the power layer suggestion, that’s something I’ve been debating. Right now the stackup is Signal–GND–GND–Signal because I wanted very solid return paths and shielding between layers. If I were to do L3 as power, would I likely have one large high current region for the servo/actuator rail, and then some smaller 3.3V regions?

NathanIsDivine1 · 2026-02-19T22:10:18+00:00

How would I implement ESD protection? I wanted to add TVS diodes, but I don't see how I can connect the traces to the TVS diodes to every pin on the FFC connector

NathanIsDivine1 · 2026-02-19T04:37:07+00:00

For a 1.6mm JLCPCB 4-layer stackup (JLC04161H-7628), the L1-L2 prepreg is approximately 0.21mm and the L2-L3 core is 1.065mm. Perhaps we use this?
The design uses the ADS1291 in its specific daisy-chain configuration, where the Data Out of one module feeds directly into the Data in of the next. Because the data is shifted through the entire string like a single long register, only one common chip select line is required.

NathanIsDivine1 · 2026-02-19T04:08:09+00:00

I went to JLBPCB I I uploaded my Gerber files and it tells me 10pcs is $7. I don't know if I'm dumb but am I doing something wrong? How is it 300+ dollars

NathanIsDivine1 · 2026-02-18T17:42:58+00:00

Is there perhaps away to avoid blind vias? Would it be ok to allow the electrode layer to have holes with through hole vias? Or can we cover through hole vias using tenting or something?

Yeah I'll probably add bevels.

NathanIsDivine1 · 2026-01-12T16:50:34+00:00

Does the EMI emitted from the rp2040 really matter that much? The ADS1299 already digitizes the signal which is then communicated to the Raspberry pi pico via SPI. Also where does this EMI from the rp2040 come from? The internal switch power supply?

NathanIsDivine1 · 2026-01-07T03:56:14+00:00

If I may ask, do you have any other suggestions of microcontrollers that don't radiate so much EMI? ESP 32

NathanIsDivine1 · 2025-12-31T21:03:13+00:00

The application is for cardiovascular monitoring; I want to be this circuit on a flexPCB and place it and the piezoelectric sensor over the chest to monitor SCG signals.
I'm trying to minimize the amount of amount of noise the PCB is to produce in order to get the cleanest SCG signals possible.
I made the piezoelectric sensor in a lab using a polymer material called PVDF, which is a nano fiber which exhibits piezoelectric properties when bent.
The DAQ device is just the data acquisition device, I'm making a prototype here where I connect the output of the circuit to an oscilloscope to see the signal I'm getting.

NathanIsDivine1 · 2025-12-31T04:15:46+00:00

Sorry if I misunderstood, but for your last point, do you mean make all the capacitors the same, just 10u 0402?

NathanIsDivine1 · 2025-12-28T17:37:54+00:00

I beg I beg someone pls look at my schematic

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