Proxy wrote:
if you're using one of those arduino CH376 modules, they're running at 3.3V which may cause occasional issues when reading from the chip. you can modify the module to run directly with 5V by simply removing the regulator and bridging the left and middle pins of where the regulator used to be.
Thanks for mentioning this. I removed the 3.3V regulator and that seems to have resolved issues I was having with the chip locking up or returning garbage data. Now I just need to play around with it and figure out how to get it working. I'm using the parallel mode and have it wired directly to my bus.
There are multiple variations of the CH376S board out there. I checked out the voltages on mine and, sure enough, VCC (pin 28) was running off a 3.3V regulator. More interestingly, V3 (pin 9) had a cap on it, but was not tied to VCC, which the datasheet says it should be for VCC=3.3V operation. The "just a cap on it" configuration is only for 5V VCC. This means the board came in a configuration that is not valid, according to the datasheet - it says that pin 9 should be tied to VCC when running the chip off 3.3V and should just have a cap to ground on it when VCC=5V.
I believe the V3 pin is an internal regulator that makes around 3V for the USB data lines (USB 2.0 power is 5V, but the data line signals run around 3 or 3.3V). When running with 3.3V VCC there wouldn't be enough voltage after the internal regulator so, when running off 3.3V for VCC, they recommend tying 3.3V directly to V3 as well (esentially bypassing the internal regulator).
For others thinking of bypassing the regulator, double check that VCC (pin28) is NOT shorted to V3 (pin 9) on your PCB. Looking at screen shots of other boards, it's hard to tell but it appears they are shorted on at least some variations of the board. For 5V operation, the V3 pin (pin 9) should only have a cap to ground on it and should NOT be tied directly to VCC (pin 28).
Here's a photo of my modified board (U2 removed and two of its pins shorted to tie VCC to 5V):
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File comment: CH376S board with regulator bypassed
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