Teensy 3.2+ ILI9341 +audio shield + 23LC1024 possible ?

[Digitana]

Hi.. can anyone let me know if it is possible to add the external ram option to a teensy 3.2 +audio shield + TFT ILI9341 combination ? I am unsure about how the SPI bus is shared between the TFT and the 23LC1024. I have teensy 3.2 +audio shield + TFT ILI9341 working fine ..but when I tried adding a single 23LC1024 to make use of AudioEffectDelayExternal it doesn't work. Probably a coding error but I just wanted to check I am not trying the impossible .. :0)

thanks for any help..

 

[GremlinWrangler]

It's certainly physically possible, since with SPI chip select manages which device is communicating, achieving it with this specific hardware may be a challange. Key issue is that you would have the audio library interrupting to read and write RAM while your display is getting updated so you might end up having to modify both libraries to properly co-operate. Second challange is that many ILI9341 controllers don't actually take their data out pin out of circuit properly (high Z), see warnings on the PJRC shop page for them from people sharing the bus with SD cards.

 

[Digitana]

It's certainly physically possible, since with SPI chip select manages which device is communicating, achieving it with this specific hardware may be a challange. Key issue is that you would have the audio library interrupting to read and write RAM while your display is getting updated so you might end up having to modify both libraries to properly co-operate. Second challange is that many ILI9341 controllers don't actually take their data out pin out of circuit properly (high Z), see warnings on the PJRC shop page for them from people sharing the bus with SD cards.

Hi..ok thanks for this. Yes I did read the issues with using SD cards + ILI9341..so the same hardware issues (and potential solutions ?) might apply to 23LC1024 I guess.

 

[Frank B]

There's space on the audio-shield where you can solder a 23LC1024 (SMD)

 

[Digitana]

There's space on the audio-shield where you can solder a 23LC1024 (SMD)

Hi Frank..yes I noticed the smd pads on the audio card. I have 2 teensy 3.2's with 2 audio cards in my project, one for synth sounds one for sound FX . I use the windbond chip on the 1st audio card for low latency sample playback of sounds copied off the sd card and the second teensy is driving the TFT and the audio FX. I have some of your memory boards ..was hoping to use them for extra long delays on the second teensy.. but since the SPI is being used by the TFT..I wonder, even if I got it working, whether it would load the spi too much. I was thinking of maybe using a third lower spec micro just for the tft display...that would free up the spi on the second teensy for your memory board...

 

[PaulStoffregen]

but since the SPI is being used by the TFT..I wonder, even if I got it working, whether it would load the spi too much.

It's supposed to work, but of course there could be possible issues. Some operations in ILI9341_t3 might hog the SPI too long. If you run into this, please post a complete program that reproduces the problem. These sorts of things only get investigated and (eventually) improved when reproducible reports are posted.

But overall, things works quite well. If you watch the last few minutes of the tutorial video, you can see the audio library is reading sound from a SD card using SPI, and also rapidly redrawing level meters on the ILI9341 TFT. That's a pretty similar test, since the audio from the SD card is stereo, so it's using approx the same bandwidth as you'll use for mono input & output to the 23LC1024. In fact, your use will be less likely to conflict, since those RAM chips don't have the access latency of SD cards.

 

[Digitana]

It's supposed to work, but of course there could be possible issues. Some operations in ILI9341_t3 might hog the SPI too long. If you run into this, please post a complete program that reproduces the problem. These sorts of things only get investigated and (eventually) improved when reproducible reports are posted.

But overall, things works quite well. If you watch the last few minutes of the tutorial video, you can see the audio library is reading sound from a SD card using SPI, and also rapidly redrawing level meters on the ILI9341 TFT. That's a pretty similar test, since the audio from the SD card is stereo, so it's using approx the same bandwidth as you'll use for mono input & output to the 23LC1024. In fact, your use will be less likely to conflict, since those RAM chips don't have the access latency of SD cards.

Hi Paul..ok many thanks..I am encouraged by your comments and will post code if I still cant figure it out. I did watch your excellent video tutorial ..just had forgot about the level meter project at the end :0) .