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Forum Index : Microcontroller and PC projects : Raspberry Pi CP2102 programming ......
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hitsware2 Guru  Joined: 03/08/2019 Location: United StatesPosts: 719 |
I have one of these ..... It works with a Pico with the UART set to MIDI baudrate and running the script. I would like to go directly from USB to the synth board. I now have this .... I think it will convert USB to MIDI , but haven't a clue how to program it ???? The code below shows a datastream ( strangely ? ) off the TX pin. import serial #Serial takes two parameters: serial device and baudrate ser = serial.Serial('/dev/ttyUSB0', 9600) while True: ser.write(bytes([144,60,127])) my site |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
The CP2102 is a USB to serial bridge. Windows sees it as a USB device and creates a COM port for it. It doesn't require programming, that's done by changing baud rate etc. on the virtual COM port that windows creates when it sees the CP2102. The baud rate for the CP2102 is set by changing the settings of the virtual COM port. The serial I/O connections on the CP2102 are at 3.3V logic levels and I suspect would need some conversion to connect to MIDI, which IIRC uses opto couplers and 5V supplies. After that you are on your own. I've no idea about the DreamBlaster. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 5090 |
Hi Hitsware, I assume you are trying to send MIDI (serial) to the module (and not parallel). The CP2102 communicates USB to a PC, where you can use a terminal program or you can use MMB4W or MMB4DOS or MMB4L to send data to it. Although the connection between the PC and the CP2102 is USB, and can use various speeds, the serial connection (UART) needs to have the correct baudrate before the MIDI module will understand. If you look at wikipedia, you can see that the serial baudrate for MIDI must be 31.25kbps. If you can set this exact baudrate in your program (Maybe the CP2102 does not support this baudrate) you should be able to send commands to the module. Connect ground to ground, and the CP2102 TX PIN TO SAM2695 (the chip) pin 16. Not sure what the module pin is. When (after careful trying) it does not work, maybe you need to invert the TX signal (the MIDI circuit is not shown in the board documentation, so I am not sure you need an inverter or not). Regards, Volhout PicomiteVGA PETSCII ROBOTS |
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| hitsware2 Guru Joined: 03/08/2019 Location: United StatesPosts: 719 |
Right .... This works with module connected to Pico : from machine import UART, Pin fo = UART(1, baudrate=31250, tx=Pin(4), rx=Pin(5)) fo.write(bytes([192,26,193,13,194,107,195,115])) my site |
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| hitsware2 Guru Joined: 03/08/2019 Location: United StatesPosts: 719 |
Click here for next best thing to the DreamBlaster...... my site |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
You need a terminal or something that will let you send bytes from the PC. Wouldn't MMB4W work doing that now? If you use Tera Term, you can see the new com port that windows makes when you connect the CP2102. Type the 31250 baud rate into Tera Term (it doesn't show it on the list as it only shows standard baud rates). Then send the ASCII characters for those decimal values. Sorry, I don't know how to do that in Tera Term unless you can type them on the keyboard. No spaces. You may have to experiment with Tera Term to find out if you need CR, LF or both. Pretty board, but as soon as I read "Arduino" I lost interest. lol Edited 2022-07-20 04:32 by Mixtel90 Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| hitsware2 Guru Joined: 03/08/2019 Location: United StatesPosts: 719 |
 ........I T W O R K S !!!!!!! ..... ######## Ten Notes From Heaven ######## import time import serial ser = serial.Serial('/dev/ttyUSB0', 31250) #print(ser.name) for i in range(10): ser.write(bytes([144,60,127])) time.sleep(0.5) ser.write(bytes([144,60,0])) time.sleep(0.5) ser.close() I didn't think the RPi would produce the right baud , but it does ! my site |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 5090 |
Again, it is not the rpi, but the cp2102 that creates the baudrate.. PicomiteVGA PETSCII ROBOTS |
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| hitsware2 Guru Joined: 03/08/2019 Location: United StatesPosts: 719 |
Unlike RS232 ? my site |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 4044 |
What?! Something along the lines of RS232 is happening but at that specific baud rate - which is being handled by the cp2102. The CPU, be it RPi or not, is using USB. Setting the baud rate involves the host (RPi/etc) telling the cp2102 what rate to use. John |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
The CP2102 includes a set of registers, a programmable baud rate generator and a UART. It transfers data over its TX and RX pins at the speed set by the baud rate generator. The host device writes to the registers on the CP2102 to define communication parameters such as baud rate. The USB link runs independently to the CP2102 TX and RX pins. It can transfer data much faster than the baud rate generator can clock the UART. RS-232 is a hardware definition for communication signals. The baud rate used isn't part of the RS-232 standard. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6283 |
Some (most), but not all USB-TTL adapters can set their baud rate to any value. Others are restricted to the 'standard' values. For some, it depends on the operating system and the drivers. Your choice of CP2102 was fortunate. Jim VK7JH MMedit |
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| hitsware2 Guru Joined: 03/08/2019 Location: United StatesPosts: 719 |
A shame to only use 3 pins .  my site |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
The CP2102 is a pretty old chip now and there are nicer alternatives. Some of the cheap boards that use it seem to be using some rather dodgy clone chips that have some very poor characteristics. Be careful with VDDout. It comes from a tiny voltage regulator and is ok for pull-up resistors but not that much more. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| hitsware2 Guru Joined: 03/08/2019 Location: United StatesPosts: 719 |
I'm using VBUS to power the synth and that works ( possibly some noise ) Maybe I should try VDD ? my site |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
VBUS is 5V from the USB. VDD out is supposed to be 3.3V, but sometimes it isn't! There have been cases of it being at 5V. The *total* current output from the regulator is supposed to be 100mA, in theory you have about 90mA available at 3.3V. Don't take this as gospel without testing it (gently) on dummy loads first as the Chinese take a remarkably flexible view of specifications. You may need to put decoupling caps from VDD to GND at the module. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| hitsware2 Guru Joined: 03/08/2019 Location: United StatesPosts: 719 |
import serial fo = serial.Serial('/dev/ttyUSB0', 31250) while True: fo.write(bytes([255])) Tried a new chip and it appeared to be working , but no music . Above test measures 3.12 kHz on working unit , but 3.85 kHz ( nearest standard ? ) on non working unit ..... my site |
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