Subfanatic
Member
Hi, Teensy warriors!
I've run into a weird T4.1 issue. Currently working on a manufactured prototype PCB with two MCUs (T4.0 and T4.1), 4 I2S/TDM ΔΣ DACs (CS42448, PCM1681, PCM3060 and WM8731), 2 SPI TFTs (ILI9225 and ILI9341), additional 8-ch ADCs on SPI2, 16 pots multiplexed with 74HC4067, etc. The power section supplies ±12V for the op-amps, two separate +5V/800mA lines for the analog section and Teensy, and 3.3V/1000mA for digital. Digital signals are separated from the analog section (their traces never cross), SPI lines are as short as possible, every single component is thoroughly decoupled with adequate caps. I use a combination of star ground and digital / analog ground planes, connected together in the very center of the PCB.
With I2S / I2S2 everything works as it should on both MCUs. 12-bit ADC readings are rock steady even without analogReadAveraging / ResponsiveAnalogRead, no problem whatsoever. With T4.0 TDM / TDM2 audio works normally, but when I switch to T4.1 (they go into the same socket, I just swap them) everything suddenly goes haywire Periodical 150-200mV spikes are appearing in the audio signal on all channels, manifesting as audio crackling and high frequency noise. ADC readings are all over the place; I have to use both analogReadAveraging(16) and ResponsiveAnalogRead with setActivityThreshold(16) to get at least somewhat stable reading: I guess the same spikes are bleeding into the ADC. I tried literally everything, made another prototype without the rest of the electronics to try and locate the problem, but it persists in the exactly same manner
T4.1 I2S audio
T4.1 TDM audio
The problem is significantly reduced if I turn off SPI, but the spikes are still audible (not nearly as much as before) and I really really need SPI
T4.0 doesn't suffer from the same problem. Here's the comparison I made on the protoboard with only Teensy and PCM1681 connected, without the ΔΣ multi-point filters and the rest of the components:
T4.0 TDM audio, unfiltered
T4.1 TDM audio, unfiltered
Please help, I've bumped into the wall and have no idea what else to try
I've run into a weird T4.1 issue. Currently working on a manufactured prototype PCB with two MCUs (T4.0 and T4.1), 4 I2S/TDM ΔΣ DACs (CS42448, PCM1681, PCM3060 and WM8731), 2 SPI TFTs (ILI9225 and ILI9341), additional 8-ch ADCs on SPI2, 16 pots multiplexed with 74HC4067, etc. The power section supplies ±12V for the op-amps, two separate +5V/800mA lines for the analog section and Teensy, and 3.3V/1000mA for digital. Digital signals are separated from the analog section (their traces never cross), SPI lines are as short as possible, every single component is thoroughly decoupled with adequate caps. I use a combination of star ground and digital / analog ground planes, connected together in the very center of the PCB.
With I2S / I2S2 everything works as it should on both MCUs. 12-bit ADC readings are rock steady even without analogReadAveraging / ResponsiveAnalogRead, no problem whatsoever. With T4.0 TDM / TDM2 audio works normally, but when I switch to T4.1 (they go into the same socket, I just swap them) everything suddenly goes haywire Periodical 150-200mV spikes are appearing in the audio signal on all channels, manifesting as audio crackling and high frequency noise. ADC readings are all over the place; I have to use both analogReadAveraging(16) and ResponsiveAnalogRead with setActivityThreshold(16) to get at least somewhat stable reading: I guess the same spikes are bleeding into the ADC. I tried literally everything, made another prototype without the rest of the electronics to try and locate the problem, but it persists in the exactly same manner
T4.1 I2S audio
T4.1 TDM audio
The problem is significantly reduced if I turn off SPI, but the spikes are still audible (not nearly as much as before) and I really really need SPI
T4.0 doesn't suffer from the same problem. Here's the comparison I made on the protoboard with only Teensy and PCM1681 connected, without the ΔΣ multi-point filters and the rest of the components:
T4.0 TDM audio, unfiltered
T4.1 TDM audio, unfiltered
Please help, I've bumped into the wall and have no idea what else to try