RP2040 SPI

[klspstck]

Good morning.

I am able to use both SPI channels on the RP2040 with success.

When using "SPI.begin(true)" each transmission is pulling down CSn for every byte.

What I havn't found, lacking documentation, is a way to send to send three or more bytes within a common CSn.

My solution is to use "SPI.begin()" and "digitalWrite(CSn, LOW/HIGH)" controlling a MCP23S17 device.

This device needs at least three bytes, ADDRCMD - REGADDR - DATA, within one CSn.

My motivation is to gain control over the registers byte wise.

Did I miss something?

Kind regards
Klaus P. Stock

[earlephilhower]

We implement the regular Arduino SPI interface. The Arduino docs and forum can help you there, and the specific Pico extensions are documented in https://arduino-pico.readthedocs.io/en/latest/spi.html

You can use the SPI.transfer(buffer, count) to do what you want using HW chip select. Something like

...
uint8_t pkt[3] = { ADDRCMD, REGADDR, DATA};
SPI.beginTransaction(spisettings);
SPI,transfer(pkt, 3);
SPI.endTransaction();
...

[klspstck]

html,body{background-color:#fff;color:#333;line-height:1.4;font-family:sans-serif,Arial,Verdana,Trebuchet MS;}Good morning Earle, thank you for the quick answer. I think I tested this approach already, but I am nit sure about it. Unfortunately I will not be able to review it until tomorrow afternoon CET. Just a suggestion: it is quite tedious to jump between different documentations. Your documentation about the RP2040 differences maybe improved by adding the redundant information aboutSPI.transfer() and SPI1.transfer(), escpecially the overloading versions. ;-)) Anyhow, please be patient. I will notify you about my observation. Kind regards Klaus P. StockStock & PartnerAdvanced Education GmbH----------------------- Earle F. Philhower, III schrieb am 18.02.2025 18:22 (GMT +01:00): We implement the regular Arduino SPI interface. The Arduino docs and forum can help you there, and the specific Pico extensions are documented in https://arduino-pico.readthedocs.io/en/latest/spi.html You can use the SPI.transferbuffer, count) to do what you want using HW chip select. Something like ... uint8_t pkt[3] = { ADDRCMD, REGADDR, DATA}; SPI.beginTransaction(spisettings); SPI,transfer(pkt, 3); SPI.endTransaction(); ... —Reply to this email directly, view it on GitHub, or unsubscribe.You are receiving this because you authored the thread.Message ID: ***@***.***>

[klspstck]

html,body{background-color:#fff;color:#333;line-height:1.4;font-family:sans-serif,Arial,Verdana,Trebuchet MS;}Hello Earle, sorry to answer late, but I was quite busy. The first picture shows what happens when using the following:   #define MCP_SPEED 10000000 #define MCP_DATA_ORDER MSBFIRST #define MCP_SPI_MODE SPI_MODE0 SPISettings MCP_setting( MCP_SPEED ,MCP_DATA_ORDER ,MCP_SPI_MODE ); setup: SPI1.setCS(MCP_CS_PIN); SPI1.setSCK(MCP_SCK_PIN); SPI1.setTX(MCP_TX_PIN); SPI1.setRX(MCP_RX_PIN);   SPI1.begin(true);   the read:     buttonState = MCP_read(GPIOB);   the function: uint8_t MCP_read(const uint8_t register_addr) { uint8_t data; uint8_t pkt[3] = { MCP_READ_CMD ,register_addr ,DUMMY_BYTE }; SPI1.beginTransaction(MCP_setting); SPI1.transfer(pkt, 3); SPI1.endTransaction();   return pkt[2]; }   Channel 1: a trigger pulse for the scope Channel 2: CSn Channel 3: COPI Channel 4; CIPO   As you can see each byte transfered has an individual CSn and nothing will be returned on CIPO.   The second picture shows what the MCP23S17 requires: One CSn for all three bytes.   I had to do it by specifying      SPI1.begin();   and in the function using a manually set LOW and HIGH for the CSn pin.      digitalWrite(MCP_CS_PIN, LOW); //enable chip select manually SPI1.beginTransaction(MCP_setting); SPI1.transfer(pkt, 3); SPI1.endTransaction(); digitalWrite(MCP_CS_PIN, HIGH); //disable chip select manually I don't know if there is any elegant solution and yes, I can live with the manual solution.   Thank you for your help.   Kind regards Klaus P. StockStock & PartnerAdvanced Education GmbH----------------------- Earle F. Philhower, III schrieb am 18.02.2025 18:22 (GMT +01:00): We implement the regular Arduino SPI interface. The Arduino docs and forum can help you there, and the specific Pico extensions are documented in https://arduino-pico.readthedocs.io/en/latest/spi.html You can use the SPI.transferbuffer, count) to do what you want using HW chip select. Something like ... uint8_t pkt[3] = { ADDRCMD, REGADDR, DATA}; SPI.beginTransaction(spisettings); SPI,transfer(pkt, 3); SPI.endTransaction(); ... —Reply to this email directly, view it on GitHub, or unsubscribe.You are receiving this because you authored the thread.Message ID: ***@***.***>